Cherry-pick 283974@main (4f4db5a). https://bugs.webkit.org/show_bug.cgi?id=279972

    [GStreamer] Do not access a null GstStructure
    https://bugs.webkit.org/show_bug.cgi?id=279972

    Reviewed by Philippe Normand.

    Stats can be null in some sinks so we avoid accessing them in that case. For the same prize we protect the access to
    null structures in the GstStructure accessors.

    * Source/WebCore/platform/graphics/gstreamer/GStreamerCommon.cpp:
    (WebCore::gstStructureGet):
    (WebCore::gstStructureGetString):
    (WebCore::gstStructureGetName):
    * Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.cpp:
    (WebCore::MediaPlayerPrivateGStreamer::updateVideoSinkStatistics):

    Canonical link: https://commits.webkit.org/283974@main

Canonical link: https://commits.webkit.org/282416.111@webkitglib/2.46

Author: calvaris

Source/WebCore/platform/graphics/gstreamer/GStreamerCommon.cpp

@@ -1019,6 +1019,11 @@ std::optional<T> gstStructureGet(const GstStructure* structure, ASCIILiteral key
 template<typename T>
 std::optional<T> gstStructureGet(const GstStructure* structure, StringView key)
 {
+    if (!structure) {
+        ASSERT_NOT_REACHED_WITH_MESSAGE("tried to access a field of a null GstStructure");
+        return std::nullopt;
+    }
+
     T value;
     auto strKey = key.toStringWithoutCopying();
     if constexpr(std::is_same_v<T, int>) {
@@ -1063,16 +1068,31 @@ template std::optional<bool> gstStructureGet(const GstStructure*, StringView key
 
 StringView gstStructureGetString(const GstStructure* structure, ASCIILiteral key)
 {
+    if (!structure) {
+        ASSERT_NOT_REACHED_WITH_MESSAGE("tried to access a field of a null GstStructure");
+        return { };
+    }
+
     return gstStructureGetString(structure, StringView { key });
 }
 
 StringView gstStructureGetString(const GstStructure* structure, StringView key)
 {
+    if (!structure) {
+        ASSERT_NOT_REACHED_WITH_MESSAGE("tried to access a field of a null GstStructure");
+        return { };
+    }
+
     return StringView::fromLatin1(gst_structure_get_string(structure, static_cast<const char*>(key.rawCharacters())));
 }
 
 StringView gstStructureGetName(const GstStructure* structure)
 {
+    if (!structure) {
+        ASSERT_NOT_REACHED_WITH_MESSAGE("tried to access a field of a null GstStructure");
+        return { };
+    }
+
     return StringView::fromLatin1(gst_structure_get_name(structure));
 }
 

Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.cpp

@@ -4301,6 +4301,9 @@ bool MediaPlayerPrivateGStreamer::updateVideoSinkStatistics()
 
     GUniqueOutPtr<GstStructure> stats;
     g_object_get(m_videoSink.get(), "stats", &stats.outPtr(), nullptr);
+    if (!stats)
+        return false;
+
     auto totalVideoFrames = gstStructureGet<uint64_t>(stats.get(), "rendered"_s);
     auto droppedVideoFrames = gstStructureGet<uint64_t>(stats.get(), "dropped"_s);