Fix dangling pointer _encoder in video_sender.cc.

When _codecDataBase.SetSendCodec() fails, the encoder may be deleted.
This is however not reflected in _encoder, which then becomes a dangling
pointer to the deleted object.

BUG=2384
R=stefan@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/2229004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@4765 4adac7df-926f-26a2-2b94-8c16560cd09d
2 files changed