fix

app/Http/Controllers/DashboardController.php

@@ -88,7 +88,10 @@ class DashboardController extends Controller
         $tweet = Tweet::where('id', $request->input('tweet_id'))->first();
         if($tweet) {
             // Calculate the previous mission status before saving this tweet
-            $previousMissionStatus = $tweet->mission->complete($tweet->team);
+            if($tweet->team)
+                $previousMissionStatus = $tweet->mission->complete($tweet->team);
+            else
+                $previousMissionStatus = false;
 
             $tweet->m1_transit_line_id = null;
             $tweet->m1_non_trimet = null;