When merging users remove the email from the user to be merged

dmp-backend/web/src/main/java/eu/eudat/logic/managers/MergeEmailConfirmationManager.java

@@ -90,6 +90,7 @@ public class MergeEmailConfirmationManager {
 			databaseRepository.getUserDmpDao().createOrUpdate(userDmp);
 		});
 		oldUser.setUserStatus((short)1);
+		oldUser.setEmail(null);
 		databaseRepository.getUserInfoDao().createOrUpdate(oldUser);
 	}