Check null and return input value in UserSelectedRecord.cs to avoid error thrown.

Author: taooceros

Flow.Launcher/Storage/UserSelectedRecord.cs

@@ -28,6 +28,11 @@ public UserSelectedRecord()
 
         private static int GenerateStaticHashCode(string s, int start = HASH_INITIAL)
         {
+            if (s == null)
+            {
+                return start;
+            }
+
             unchecked
             {
                 // skip the empty space
@@ -101,4 +106,4 @@ public int GetSelectedCount(Result result)
             return selectedCount;
         }
     }
-}
+}