App crashing only on Device - swift

Question

This strange crash happens only running on Devices, while in simulator works normally.
Debugging line by line, i noticed that it occurs while i append a String Value to an Array of Doubles. To do that i convert the double using an extension:
extension String {
func toDouble() -> Double? {
return NSNumberFormatter().numberFromString(self)?.doubleValue
}
}
So the crashing line is:
litros.append(temp_litros.toDouble()!) //litros is my array and temp_litros my string
the error:
fatal error: unexpectedly found nil while unwrapping an Optional value
I really don't understand why it works in simulator and it doesn't on devices.
Anyone have an ideia what could be happening here? Thanks in advance!
Crash Report:
Incident Identifier: 49F378A2-E7D9-4985-B208-99F529AE8813
CrashReporter Key: fe58b29412047d4d8980b9cb66ae017f1c2db7d5
Hardware Model: iPhone7,2
Process: Nuvem [9479]
Path: /private/var/mobile/Containers/Bundle/Application/8989627A-4064-428C-888B-C09F00A3EA0B/Nuvem.app/Nuvem
Identifier: br.com.gimenez.Nuvem
Version: 1 (1.0)
Code Type: ARM-64 (Native)
Parent Process: launchd [1]
Date/Time: 2015-07-23 18:07:12.529 -0300
Launch Time: 2015-07-23 18:07:05.037 -0300
OS Version: iOS 8.4 (12H143)
Report Version: 105
Exception Type: EXC_BREAKPOINT (SIGTRAP)
Exception Codes: 0x0000000000000001, 0x0000000100659474
Triggered by Thread: 0
Thread 0 name: Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0 libswiftCore.dylib 0x0000000100659474 0x100598000 + 791668
1 Nuvem 0x00000001000b5110 Nuvem.GraficoViewController.viewDidLoad (Nuvem.GraficoViewController)() -> () (GraficoViewController.swift:69)
2 Nuvem 0x00000001000b5410 #objc Nuvem.GraficoViewController.viewDidLoad (Nuvem.GraficoViewController)() -> () (GraficoViewController.swift:0)
3 UIKit 0x0000000188d14c14 -[UIViewController loadViewIfRequired] + 688
4 UIKit 0x0000000188d14924 -[UIViewController view] + 28
5 UIKit 0x0000000188eb71ec -[UINavigationController _startCustomTransition:] + 708
6 UIKit 0x0000000188dc9e80 -[UINavigationController _startDeferredTransitionIfNeeded:] + 464
7 UIKit 0x0000000188dc9c4c -[UINavigationController __viewWillLayoutSubviews] + 52
8 UIKit 0x0000000188dc9bcc -[UILayoutContainerView layoutSubviews] + 196
9 UIKit 0x0000000188d116f0 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 576
10 QuartzCore 0x000000018864ddb4 -[CALayer layoutSublayers] + 148
11 QuartzCore 0x000000018864881c CA::Layer::layout_if_needed(CA::Transaction*) + 316
12 QuartzCore 0x00000001886486c0 CA::Layer::layout_and_display_if_needed(CA::Transaction*) + 28
13 QuartzCore 0x0000000188647e54 CA::Context::commit_transaction(CA::Transaction*) + 272
14 QuartzCore 0x0000000188647bd4 CA::Transaction::commit() + 524
15 QuartzCore 0x00000001886412fc CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) + 76
16 CoreFoundation 0x00000001842542a0 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 28
17 CoreFoundation 0x000000018425122c __CFRunLoopDoObservers + 356
18 CoreFoundation 0x000000018425160c __CFRunLoopRun + 832
19 CoreFoundation 0x000000018417d2d0 CFRunLoopRunSpecific + 392
20 GraphicsServices 0x000000018dbd36f8 GSEventRunModal + 164
21 UIKit 0x0000000188d7af3c UIApplicationMain + 1484
22 Nuvem 0x00000001000ad9b8 main (AppDelegate.swift:14)
23 libdyld.dylib 0x0000000196612a04 start + 0
Thread 1 name: Dispatch queue: com.apple.libdispatch-manager
Thread 1:
0 libsystem_kernel.dylib 0x0000000196710c24 kevent64 + 8
1 libdispatch.dylib 0x00000001965f5e6c _dispatch_mgr_invoke + 272
2 libdispatch.dylib 0x00000001965e7998 _dispatch_mgr_thread + 48
Thread 2:
0 libsystem_kernel.dylib 0x000000019672bc78 __workq_kernreturn + 8
1 libsystem_pthread.dylib 0x00000001967c52d8 _pthread_wqthread + 988
2 libsystem_pthread.dylib 0x00000001967c4eec start_wqthread + 0
Thread 3:
0 libsystem_kernel.dylib 0x000000019672bc78 __workq_kernreturn + 8
1 libsystem_pthread.dylib 0x00000001967c52d8 _pthread_wqthread + 988
2 libsystem_pthread.dylib 0x00000001967c4eec start_wqthread + 0
Thread 4:
0 libsystem_kernel.dylib 0x000000019672bc78 __workq_kernreturn + 8
1 libsystem_pthread.dylib 0x00000001967c52d8 _pthread_wqthread + 988
2 libsystem_pthread.dylib 0x00000001967c4eec start_wqthread + 0
Thread 5:
0 libsystem_kernel.dylib 0x000000019672bc78 __workq_kernreturn + 8
1 libsystem_pthread.dylib 0x00000001967c52d8 _pthread_wqthread + 988
2 libsystem_pthread.dylib 0x00000001967c4eec start_wqthread + 0
Thread 6 name: com.apple.NSURLConnectionLoader
Thread 6:
0 libsystem_kernel.dylib 0x0000000196710e0c mach_msg_trap + 8
1 libsystem_kernel.dylib 0x0000000196710c84 mach_msg + 68
2 CoreFoundation 0x0000000184253720 __CFRunLoopServiceMachPort + 196
3 CoreFoundation 0x0000000184251674 __CFRunLoopRun + 936
4 CoreFoundation 0x000000018417d2d0 CFRunLoopRunSpecific + 392
5 CFNetwork 0x0000000183c5a590 +[NSURLConnection(Loader) _resourceLoadLoop:] + 436
6 Foundation 0x000000018519ddb4 __NSThread__main__ + 1068
7 libsystem_pthread.dylib 0x00000001967c7dc4 _pthread_body + 160
8 libsystem_pthread.dylib 0x00000001967c7d20 _pthread_start + 156
9 libsystem_pthread.dylib 0x00000001967c4ef4 thread_start + 0
Thread 7 name: com.apple.CFSocket.private
Thread 7:
0 libsystem_kernel.dylib 0x000000019672b498 __select + 8
1 CoreFoundation 0x0000000184259124 __CFSocketManager + 668
2 libsystem_pthread.dylib 0x00000001967c7dc4 _pthread_body + 160
3 libsystem_pthread.dylib 0x00000001967c7d20 _pthread_start + 156
4 libsystem_pthread.dylib 0x00000001967c4ef4 thread_start + 0
Thread 8:
0 libsystem_kernel.dylib 0x000000019672bc78 __workq_kernreturn + 8
1 libsystem_pthread.dylib 0x00000001967c52d8 _pthread_wqthread + 988
2 libsystem_pthread.dylib 0x00000001967c4eec start_wqthread + 0
Thread 9:
0 libsystem_kernel.dylib 0x000000019672bc78 __workq_kernreturn + 8
1 libsystem_pthread.dylib 0x00000001967c52d8 _pthread_wqthread + 988
2 libsystem_pthread.dylib 0x00000001967c4eec start_wqthread + 0
Thread 10:
0 libsystem_kernel.dylib 0x000000019672bc78 __workq_kernreturn + 8
1 libsystem_pthread.dylib 0x00000001967c52d8 _pthread_wqthread + 988
2 libsystem_pthread.dylib 0x00000001967c4eec start_wqthread + 0
Thread 11:
0 libsystem_kernel.dylib 0x000000019672bc78 __workq_kernreturn + 8
1 libsystem_pthread.dylib 0x00000001967c52d8 _pthread_wqthread + 988
2 libsystem_pthread.dylib 0x00000001967c4eec start_wqthread + 0
Thread 12:
0 libsystem_kernel.dylib 0x0000000196710e0c mach_msg_trap + 8
1 libsystem_kernel.dylib 0x0000000196710c84 mach_msg + 68
2 CoreFoundation 0x0000000184253720 __CFRunLoopServiceMachPort + 196
3 CoreFoundation 0x0000000184251674 __CFRunLoopRun + 936
4 CoreFoundation 0x000000018417d2d0 CFRunLoopRunSpecific + 392
5 Foundation 0x00000001850b54c4 -[NSRunLoop(NSRunLoop) runMode:beforeDate:] + 312
6 Foundation 0x000000018510f80c -[NSRunLoop(NSRunLoop) run] + 92
7 Nuvem 0x00000001000e64f8 +[PBAFURLConnectionOperation networkRequestThreadEntryPoint:] (PBAFURLConnectionOperation.m:151)
8 Foundation 0x000000018519ddb4 __NSThread__main__ + 1068
9 libsystem_pthread.dylib 0x00000001967c7dc4 _pthread_body + 160
10 libsystem_pthread.dylib 0x00000001967c7d20 _pthread_start + 156
11 libsystem_pthread.dylib 0x00000001967c4ef4 thread_start + 0
Thread 0 crashed with ARM Thread State (64-bit):
x0: 0x0000000100588b80 x1: 0x00000001742f6a00 x2: 0x0000000000000008 x3: 0x0000000196765a74
x4: 0x000000016fd80e38 x5: 0x0000000000000020 x6: 0x0000000000000000 x7: 0x0000000000000fa0
x8: 0x00000001742f6b80 x9: 0x0000000000000000 x10: 0x0000000100584800 x11: 0x00000000005d0bda
x12: 0x00000000fffffff2 x13: 0x00000001887c5480 x14: 0x0000000000000053 x15: 0x000000000000004d
x16: 0x00000001967bda50 x17: 0x0000000000000000 x18: 0x0000000000000000 x19: 0x0000000144d85300
x20: 0x00000001978b7720 x21: 0x0000000000000008 x22: 0x0000000000000008 x23: 0x0000000000000000
x24: 0x0000000000000006 x25: 0x000000000004ffff x26: 0x0000000144e161d0 x27: 0x000000016fd810e9
x28: 0x0000000144d85300 fp: 0x000000016fd80ed0 lr: 0x0000000100659474
sp: 0x000000016fd80ec0 pc: 0x0000000100659474 cpsr: 0x60000000

Answer 1

By default NSNumberFormatter converts data according to current locale settings. In case of simulator it uses US locale and "." as decimal separator. In case of your device it uses "," as separator so it can't convert your data and numberFromString returns nil.
Try this:
extension String {
func toDouble() -> Double? {
let formatter = NSNumberFormatter()
formatter.locale = NSLocale(localeIdentifier: "en_US")
return formatter.numberFromString(self)?.doubleValue
}
}