dispose animation controller in lock button

Author: esarbanis

packages/stream_chat_flutter/lib/src/message_input/audio_message_send_button/stream_audio_message_overlays.dart

@@ -83,6 +83,12 @@ class _LockButtonState extends State<_LockButton>
     _controller.forward();
   }
 
+  @override
+  void dispose() {
+    _controller.dispose();
+    super.dispose();
+  }
+
   @override
   Widget build(BuildContext context) {
     final audioRecordingMessageTheme = AudioRecordingMessageTheme.of(context);