Check for SB being avail before filing #668 (#669)

app/Http/Controllers/Frontend/PirepController.php

@@ -350,11 +350,12 @@ class PirepController extends Controller
 
         if ($request->has('sb_id')) {
             $brief = SimBrief::find($request->input('sb_id'));
-
+            if ($brief !== null) {
                 /** @var SimBriefService $sbSvc */
                 $sbSvc = app(SimBriefService::class);
                 $sbSvc->attachSimbriefToPirep($pirep, $brief);
             }
+        }
 
         // Depending on the button they selected, set an initial state
         // Can be saved as a draft or just submitted