LibGfx: Support AVIF images with missing pixi property

Author: https://github.com/Psychpsyo
Commit: b22341fc77
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2270
Reviewed-by: https://github.com/tcl3 ✅

Tests/LibGfx/TestImageDecoder.cpp

@@ -1067,3 +1067,9 @@ TEST_CASE(test_avif_frame_out_of_bounds)
     auto frame1 = TRY_OR_FAIL(plugin_decoder->frame(0));
     EXPECT(plugin_decoder->frame(1).is_error());
 }
+
+TEST_CASE(test_avif_missing_pixi_property)
+{
+    auto file = TRY_OR_FAIL(Core::MappedFile::map(TEST_INPUT("avif/missing-pixi-property.avif"sv)));
+    EXPECT(Gfx::AVIFImageDecoderPlugin::sniff(file->bytes()));
+}