DOS / potential heap overwrite in mkv demuxing using HEADERSTRIP decompression

DOS / potential heap overwrite in mkv demuxing using HEADERSTRIP decompression. Integer overflow in matroskaparse element in gst_matroska_decompress_data function which causes a heap overflow. Due to restrictions on chunk sizes in the matroskademux element, the overflow can't be triggered, however the matroskaparse element has no size checks.