[BUGFIX] Return true, if enddate is not given

Classes/Domain/Model/Election.php

@@ -192,6 +192,9 @@ class Election extends AbstractEntity
      */
     public function isElectionFinished()
     {
+        if ($this->getEndDate()===NULL) {
+            return true;
+        }
         if ($this->getEndDate()->getTimestamp() < time()) {
             return true;
         } else {