TrackConfiguration: report the correct FPS even if the WebM FrameRate value is missing
<rdar://problem/109161531>
Pull request: https://github.com/WebKit/WebKit/pull/13733
Committed 263964@main (3a68fc73d42a): <https://commits.webkit.org/263964@main> Reviewed commits have been landed. Closing PR #13733 and removing active labels.