Null check self.session after calling _cancel instead of before
Created attachment 434867 [details] Patch
<rdar://problem/79224868>
Comment on attachment 434867 [details] Patch r=me
Committed r280623 (240236@main): <https://commits.webkit.org/240236@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 434867 [details].