In RTPSenderVideoFrameTransformerDelegate::TransformFrame(), the encoder queue might still be null when a frame queued by a previous delegate arrives. This could happen in the context of renegotiation that results in a codec reset. In this case, the frame should be dropped. Bug: webrtc:12691 Change-Id: Ib738ce31738cffc7e01053dbc82237f457fc2286 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/216393 Commit-Queue: Guido Urdaneta <guidou@webrtc.org> Reviewed-by: Danil Chapovalov <danilchap@webrtc.org> Cr-Commit-Position: refs/heads/master@{#33866}