last fix pls?

Author: mythz

src/ServiceStack.OrmLite/Dapper/SqlMapper.Async.cs

@@ -770,7 +770,7 @@ public static async Task<GridReader> QueryMultipleAsync(this IDbConnection cnn,
                         { /* don't spoil the existing exception */ }
                     reader.Dispose();
                 }
-                cmd?.Dispose();
+                if (cmd != null) cmd.Dispose();
                 if (wasClosed) cnn.Close();
                 throw;
             }