Override FILES references.data with fallback - typo3

Question

I get the images for a slider via data = level media:-1,slide
On a news-single-page I want to use the news-images instead of. So I put the code for this in conditions [globalVar = GP:tx_news_pi1|news > 0] and get the images of the news. All ok. But I want to show the level media, if there is no news-image. How can I do this?
Here’s the TypoScript:
lib.keyVisual = COA
lib.keyVisual {
10 = FILES
10 {
references {
data = levelmedia:-1,slide
}
renderObj = COA
renderObj.10 = IMAGE
renderObj.10 {
file {
import.data = file:current:uid
treatIdAsReference = 1
width = {$keyVisualWidth}
#width.field >
height = {$keyVisualHeight}
}
}
renderObj.20 = COA
renderObj.20 {
1 = TEXT
1 {
data = file:current:title
required = 1
wrap = <h3>|</h3>
}
2 = TEXT
2 {
data = file:current:description
required = 1
wrap = <p>|</p>
}
stdWrap.wrap = <div class="imageCaptionBox">|</div>
stdWrap.required = 1
}
renderObj.wrap = <li>|</li>
}
wrap = <section id="keyvisual" class="keyvisual fullWidth"><ul class="slider nav">|</ul></section>
}
[globalVar = GP:tx_news_pi1|news > 0]
lib.keyVisual {
10 {
references {
data >
table = tx_news_domain_model_news
uid.data = GP:tx_news_pi1|news
fieldName = fal_media
}
# only images with showinpreview
renderObj.if {
value = 1
equals.data = file:current:showinpreview
}
}
}
[global]

Answer 1

Work with the ifEmpty stdWrap option.
If your COA is empty you can render the default image with this option.
simple example to explain:
[globalVar = GP:tx_news_pi1|news > 0]
lib.keyVisual {
stdWrap.ifEmpty.cObject < .10
#overrides for news picture
10 {
...
}
}
[global]

Answer 2

all conditions have an [else] so you do not need to redefine.
[globalVar = GP:tx_news_pi1|news > 0]
lib.keyVisual {
... from news...
}
[else]
lib.keyVisual {
... from levelmedia ...
}
[global]
then you need to distinguish wether an image is availabel for the news.
[globalVar = GP:tx_news_pi1|news > 0]
lib.keyVisual = COA
lib.keyVisual {
10 = CONTENT
10 {
// get news record and then get file
... from news...
if.empty.field = media
}
20 = FILES
20 {
... from levelmedia ...
if {
empty.field = media
negate = 1
}
}
}
[else]
lib.keyVisual {
... from levelmedia ...
}
[global]
that could be optimized by using a temp object for the levelmedia usage which gets copied.
temp.levelmediaImage {
...
}
[globalVar = GP:tx_news_pi1|news > 0]
kib.keyVisual = COA
lib.keyVisual {
10 = CONTENT
10 {
// get news record and then get file
... from news...
if.empty.field = media
}
20 < temp.levelmediaImage
20 {
if {
empty.field = media
negate = 1
}
}
}
[else]
lib.keyVisual < temp.levelmediaImage
[global]