Error on iPhone but not on the simulator - swift

Question

Since today i was running my app on Simulator with the 6s on iOS 10, but now I am running it on the iPhone 7. It shows me the following error when i press the Save button: Thread 1: EXC_BREAKPOINT (code=1, subcode=0x000cfba4)
My code look like this:
#IBAction func SaveAction(_ sender: AnyObject) {
let dataString = DateTextfield.text
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "MMM d, yyyy"
// convert string into date
let dateValue:NSDate? = dateFormatter.date(from: dataString!) as NSDate?
let nowDouble = dateValue?.timeIntervalSince1970
let hey = Int64(nowDouble!*1000) //Here is the error
let newdouble = Double(hey)
MyArray[Work]!["Date"]?.append(newdouble)
}
In the iOS simulator it works fine it saves the newdouble correctly to the dictionary named MyArray
If i run the app with Build Configuration: Debug
libswiftCore.dylib`function signature specialization <preserving fragile attribute, Arg[2] = Dead, Arg[3] = Dead> of Swift._fatalErrorMessage (Swift.StaticString, Swift.StaticString, Swift.StaticString, Swift.UInt, flags : Swift.UInt32) -> Swift.Never:
0x100385174 <+0>: stp x26, x25, [sp, #-80]!
0x100385178 <+4>: stp x24, x23, [sp, #16]
0x10038517c <+8>: stp x22, x21, [sp, #32]
0x100385180 <+12>: stp x20, x19, [sp, #48]
0x100385184 <+16>: stp x29, x30, [sp, #64]
0x100385188 <+20>: add x29, sp, #64 ; =64
0x10038518c <+24>: mov x19, x6
0x100385190 <+28>: mov x20, x5
0x100385194 <+32>: mov x21, x4
0x100385198 <+36>: mov x22, x3
0x10038519c <+40>: mov x23, x2
0x1003851a0 <+44>: mov x24, x1
0x1003851a4 <+48>: mov x25, x0
0x1003851a8 <+52>: adr x8, #936952 ; protocol descriptor for Swift.CVarArg + 88
0x1003851ac <+56>: nop
0x1003851b0 <+60>: add x0, x8, #16 ; =16
0x1003851b4 <+64>: movz w1, #0x28
0x1003851b8 <+68>: orr w2, wzr, #0x7
0x1003851bc <+72>: bl 0x1003854a0 ; rt_swift_allocObject
0x1003851c0 <+76>: mov x8, x0
0x1003851c4 <+80>: stp x22, x21, [x8, #16]
0x1003851c8 <+84>: strb w20, [x8, #32]
0x1003851cc <+88>: str w19, [x8, #36]
0x1003851d0 <+92>: adr x3, #241008 ; partial apply forwarder for Swift.(_fatalErrorMessage (Swift.StaticString, Swift.StaticString, Swift.StaticString, Swift.UInt, flags : Swift.UInt32) -> Swift.Never).(closure #2)
0x1003851d4 <+96>: nop
0x1003851d8 <+100>: mov x0, x25
0x1003851dc <+104>: mov x1, x24
0x1003851e0 <+108>: mov x2, x23
0x1003851e4 <+112>: mov x4, x8
0x1003851e8 <+116>: bl 0x100278b70 ; function signature specialization <preserving fragile attribute, Arg[1] = [Closure Propagated : reabstraction thunk helper from #callee_owned (#unowned Swift.UnsafeBufferPointer<Swift.UInt8>) -> () to #callee_owned (#unowned Swift.UnsafeBufferPointer<Swift.UInt8>) -> (#out ()), Argument Types : [#callee_owned (#unowned Swift.UnsafeBufferPointer<Swift.UInt8>) -> ()]> of generic specialization <preserving fragile attribute, ()> of Swift.StaticString.withUTF8Buffer <A> ((Swift.UnsafeBufferPointer<Swift.UInt8>) -> A) -> A
-> 0x1003851ec <+120>: brk #0x1 //Error message here