Merge branch '193-das-reindexieren-scheint-falsche-metadaten-zuzuordnen' into 'development'

Add null checks

See merge request sharing/codeability-sharing-platform!68

src/main/webapp/app/exercise/exercise-details/exercise-details.component.ts

@@ -107,9 +107,13 @@ export class ExerciseDetailsComponent implements OnInit, OnDestroy {
   hasChildren(): boolean {
     return (
       this.exercise !== undefined &&
+      this.exercise !== null &&
       this.exercise.originalResult !== undefined &&
+      this.exercise.originalResult !== null &&
       this.exercise.originalResult.file !== undefined &&
+      this.exercise.originalResult.file !== null &&
       this.exercise.originalResult.file.children !== undefined &&
+      this.exercise.originalResult.file.children !== null &&
       this.exercise.originalResult.file.children.length > 0
     );
   }