Return nil from RTCPeerConnectionFactory when creation fails

webrtc/sdk/objc/Framework/Classes/RTCPeerConnection.mm

 /*
  *  Copyright 2015 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 214 matching lines @@
   if (self = [super init]) {
     _observer.reset(new webrtc::PeerConnectionDelegateAdapter(self));
     std::unique_ptr<webrtc::MediaConstraints> nativeConstraints =
         constraints.nativeConstraints;
     _peerConnection =
         factory.nativeFactory->CreatePeerConnection(*config,
                                                     nativeConstraints.get(),
                                                     nullptr,
                                                     nullptr,
                                                     _observer.get());
+    if (!_peerConnection) {
+      return nil;
+    }
     _localStreams = [[NSMutableArray alloc] init];
     _delegate = delegate;
   }
   return self;
 }
 
 - (NSArray *)localStreams {
   return [_localStreams copy];
 }
 
@@ skipping 335 matching lines @@
     case RTCStatsOutputLevelDebug:
       return webrtc::PeerConnectionInterface::kStatsOutputLevelDebug;
   }
 }
 
 - (rtc::scoped_refptr<webrtc::PeerConnectionInterface>)nativePeerConnection {
   return _peerConnection;
 }
 
 @end