tag: id3v2: fix frame size check and potential invalid reads

Check the right variable when checking if there's
enough data left to read the frame size.

Closes https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/issues/876

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/-/merge_requests/1068>

gst-libs/gst/tag/id3v2frames.c

@@ -109,7 +109,7 @@ id3v2_parse_frame (ID3TagsWorking * work)
 
   if (work->frame_flags & (ID3V2_FRAME_FORMAT_COMPRESSION |
           ID3V2_FRAME_FORMAT_DATA_LENGTH_INDICATOR)) {
-    if (work->hdr.frame_data_size <= 4)
+    if (frame_data_size <= 4)
       return FALSE;
     if (ID3V2_VER_MAJOR (work->hdr.version) == 3) {
       work->parse_size = GST_READ_UINT32_BE (frame_data);