Fix exception when no citekey is present (#2904)

CHANGELOG.md

@@ -34,6 +34,7 @@ We refer to [GitHub issues](https://github.com/JabRef/jabref/issues) by using `#
 - We fixed a bug that only allowed parsing positive timezones from a FileAnnotation [#2839](https://github.com/JabRef/jabref/issues/2839)
 - We fixed a bug that did not allow the correct re-export of the MS-Office XML field `msbib-accessed` with a different date format [#2859](https://github.com/JabRef/jabref/issues/2859).
 - We fixed some bugs that prevented the display of FileAnnotations that were created using the Foxit Reader. [#2839, comment](https://github.com/JabRef/jabref/issues/2839#issuecomment-302058227).
+- We fixed an error that prevented the FileAnnotation tab to load when the entry had no bibtexkey [#2903](https://github.com/JabRef/jabref/issues/2903).
 ### Removed
 
 

src/main/java/org/jabref/logic/pdf/FileAnnotationCache.java

@@ -38,12 +38,12 @@ public Map<String, List<FileAnnotation>> load(BibEntry entry) throws Exception {
      * @return Map containing a list of annotations in a list for each file
      */
     public Map<String, List<FileAnnotation>> getFromCache(BibEntry entry) {
-        LOGGER.debug(String.format("Loading Bibentry '%s' from cache.", entry.getField(BibEntry.KEY_FIELD).get()));
+        LOGGER.debug(String.format("Loading Bibentry '%s' from cache.", entry.getCiteKeyOptional().orElse(entry.getId())));
         return annotationCache.getUnchecked(entry);
     }
 
     public void remove(BibEntry entry) {
-        LOGGER.debug(String.format("Deleted Bibentry '%s' from cache.", entry.getField(BibEntry.KEY_FIELD).get()));
+        LOGGER.debug(String.format("Deleted Bibentry '%s' from cache.", entry.getCiteKeyOptional().orElse(entry.getId())));
         annotationCache.invalidate(entry);
     }
 }