Fix exception when no merge requests are present

managetests/app.py

@@ -75,7 +75,7 @@ class TestsManager:
 
         # Load also new branches from merge requests
         new = self.gitlab.merge_requests()
-        if not new:
+        if new is None:
             raise RuntimeError("Can't get merge requests from GitLab!")
         for request in new:
             # Skip already loaded requests