File Annotation Tab fails to load if entry has not BibTexKey

[Siedlerchr]

Have an entry with no key
Add a pdf
click on File Annotations Tab:

20:32:32.914 [JavaFX Application Thread] ERROR org.jabref.FallbackExceptionHandler - Uncaught exception Occurred in Thread[JavaFX Application Thread,5,main]
java.util.NoSuchElementException: No value present
	at java.util.Optional.get(Optional.java:135) ~[?:1.8.0_131]
	at org.jabref.logic.pdf.FileAnnotationCache.getFromCache(FileAnnotationCache.java:41) ~[bin/:?]
	at org.jabref.gui.entryeditor.FileAnnotationTab.addAnnotations(FileAnnotationTab.java:101) ~[bin/:?]
	at org.jabref.gui.entryeditor.FileAnnotationTab.initialize(FileAnnotationTab.java:331) ~[bin/:?]
	at org.jabref.gui.entryeditor.EntryEditorTab.notifyAboutFocus(EntryEditorTab.java:23) ~[bin/:?]
	at org.jabref.gui.entryeditor.EntryEditor.lambda$1(EntryEditor.java:171) ~[bin/:?]
	at org.fxmisc.easybind.EasyBind.lambda$subscribe$12(EasyBind.java:263) ~[easybind-1.0.3.jar:?]