frame_types=null is a valid input for Encoder(). VP8/VP9/H264 software encoder wrappers can handle frame_types=null. Bug: b/261160916, webrtc:14852 Change-Id: I96ed98d553546ecbe70ff0356f314496f838c535 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/293260 Reviewed-by: Rasmus Brandt <brandtr@webrtc.org> Commit-Queue: Sergey Silkin <ssilkin@webrtc.org> Cr-Commit-Position: refs/heads/main@{#39325}