fix(lms): add safeguard to LmsUserlist dispatch running twice, thus ending LMS prematurely

src/Jobs/Handler/LMS.hs

@@ -304,7 +304,7 @@ dispatchJobLmsUserlist :: QualificationId -> JobHandler UniWorX
 dispatchJobLmsUserlist qid = JobHandlerAtomic act
   where
     act :: YesodJobDB UniWorX ()
-    act = do
+    act = whenM (exists [LmsUserlistQualification ==. qid]) $ do -- safeguard against multiple calls, which would close all learners due to first case below
       now <- liftIO getCurrentTime              
       -- result :: [(Entity LmsUser, Entity LmsUserlist)]
       results <- E.select $ do