Flutter analyze fix

Author: Mikael Wills

lib/src/sip_ua_helper.dart

@@ -3,6 +3,7 @@ import 'dart:async';
 import 'package:flutter_webrtc/flutter_webrtc.dart';
 import 'package:logger/logger.dart';
 import 'package:sdp_transform/sdp_transform.dart' as sdp_transform;
+import 'package:sip_ua/src/uri.dart';
 
 import 'config.dart';
 import 'constants.dart' as DartSIP_C;