Merge pull request #824 from appwrite/fix-200-concurrent-modification

Fix concurrent modification error when closing socket

Author: lohanidamodar

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

@@ -87,8 +87,8 @@ mixin RealtimeMixin {
             break;
         }
       }, onDone: () {
-        if (!_notifyDone || _creatingSocket) return;
-        for (var subscription in _subscriptions.values) {
+        final subscriptions = List.from(_subscriptions.values);
+        for (var subscription in subscriptions) {
           subscription.close();
         }
         _channels.clear();