Fix bug in MediaFormatReader::copyTrackArray() found by new libcpp assertions.
<rdar://104967552>
Pull request: https://github.com/WebKit/WebKit/pull/9541
Committed 259794@main (d7a2a7053e05): <https://commits.webkit.org/259794@main> Reviewed commits have been landed. Closing PR #9541 and removing active labels.