Resolve "Sharing Plattform: Prüfung: Gitlab Login für Simon in Produktion funktioniert nicht zuverlässig."

Related to #501 (closed)

src/main/java/at/ac/uibk/gitsearch/repository/search/ElasticSearchRepository.java

@@ -78,10 +78,14 @@ public class ElasticSearchRepository {
         return i.index(index).id(exerciseId).document(document);
       });
     final String exerciseId2 = document.getExerciseId();
-    try {
-      ExerciseId parsedId = ExerciseId.fromString(exerciseId2);
-    } catch (ParseException e) {
-      LOGGER.error("Somehow we got an corrupt exerciseId {}", exerciseId2, e);
+    if (exerciseId2 == null) {
+      LOGGER.error("Somehow we got an empty exerciseId in {}", document);
+    } else {
+      try {
+        ExerciseId.fromString(exerciseId2);
+      } catch (ParseException e) {
+        LOGGER.error("Somehow we got an corrupt exerciseId {}", exerciseId2, e);
+      }
     }
     return exerciseId2;
   }
@@ -158,9 +162,13 @@ public class ElasticSearchRepository {
    * @throws ElasticsearchException
    * @throws IOException
    */
+  @SuppressWarnings("null")
   public SearchResultDTO get(final String docId) throws IOException {
     final GetResponse<SearchResultDTO> searchResultDTOResponse =
       this.elasticsearchAPIClient.get(r -> r.index(SearchRepositoryConstants.INDEX_METADATA).id(docId), SearchResultDTO.class);
+    if (searchResultDTOResponse.source() != null) {
+      searchResultDTOResponse.source().setExerciseId(docId);
+    }
     return searchResultDTOResponse.source();
   }