[Mac wk1] http/tests/media/fairplay/fps-mse-play-while-not-in-dom.htm…

…l is a consistent crash

https://bugs.webkit.org/show_bug.cgi?id=271910
rdar://125380872

Reviewed by Eric Carlson.

In WebKitLegacy, an error can synchronously fire during enqueueSampleBuffer(), which can cause
the HTMLMediaElement to move to an error state, and its MediaSource will subsequently become
disconnected and close. This causes `m_videoRenderer` to become null after a null check.

This should likely be addressed by enqueueing the error to be executed during the next run loop.
Short term, however, is to detect that `m_videoRenderer` has become null and return early.

* Source/WebCore/platform/graphics/avfoundation/objc/SourceBufferPrivateAVFObjC.mm:
(WebCore::SourceBufferPrivateAVFObjC::enqueueSampleBuffer):

Canonical link: https://commits.webkit.org/276848@main

Source/WebCore/platform/graphics/avfoundation/objc/SourceBufferPrivateAVFObjC.mm

@@ -1092,6 +1092,10 @@ static inline bool shouldAddContentKeyRecipients()
     WebSampleBufferVideoRendering *renderer = nil;
     if (m_videoRenderer) {
         m_videoRenderer->enqueueSample(sample.platformSample().sample.cmSampleBuffer, !sample.isNonDisplaying());
+
+        // Enqueuing a sample for display my synchronously fire an error, which can cause m_videoRenderer to become null.
+        if (!m_videoRenderer)
+            return;
         renderer = m_videoRenderer->renderer();
 #if HAVE(AVSAMPLEBUFFERDISPLAYLAYER_READYFORDISPLAY)
         if (AVSampleBufferDisplayLayer *displayLayer = m_videoRenderer->displayLayer()) {