The WebGL code for finding the GraphicsClient doesn't handle the case where we're an OffscreenCanvas, but running on the main thread.
<rdar://problem/103572325>
Pull request: https://github.com/WebKit/WebKit/pull/7938
Committed 258222@main (301e966c8ef8): <https://commits.webkit.org/258222@main> Reviewed commits have been landed. Closing PR #7938 and removing active labels.