refactor(systems/gitlab): TicketSystem: add missing check for null-on-error config

src/main/java/de/hftstuttgart/unifiedticketing/systems/gitlab/GitlabTicketSystem.java

@@ -113,7 +113,11 @@ public class GitlabTicketSystem extends TicketSystem<GitlabTicket, GitlabTicketS
             .get();
 
         if (ret == null) return null;
-        else if (ret.size() != 1) throw new UnifiedticketingException("more or less than 1 dedicated ticket found");
+        else if (ret.size() != 1)
+        {
+            if (getConfigTrue(ConfigurationOptions.RETURN_NULL_ON_ERROR)) return null;
+            else throw new UnifiedticketingException("more or less than 1 dedicated ticket found");
+        }
         else return ret.get(0);
     }