Fix possible null reference when query is cancelled

Flow.Launcher/Storage/TopMostRecord.cs

@@ -18,7 +18,7 @@ internal bool IsTopMost(Result result)
             }
 
             // since this dictionary should be very small (or empty) going over it should be pretty fast.
-            return records[result.OriginQuery.RawQuery].Equals(result);
+            return result.OriginQuery != null && records[result.OriginQuery.RawQuery].Equals(result);
         }
 
         internal void Remove(Result result)