do not close subscription if creating socket is true

do not close subscription if creating socket is true to prevent concurrent modification error

Author: lohanidamodar

templates/flutter/lib/src/realtime_mixin.dart.twig

@@ -88,7 +88,7 @@ mixin RealtimeMixin {
             break;
         }
       }, onDone: () {
-        if (!_notifyDone) return;
+        if (!_notifyDone || _creatingSocket) return;
         for (var subscription in _subscriptions.values) {
           subscription.close();
         }