gstreamer/gst-discoverer: Negative-size-param in gst_buffer_fill

Project: https://anongit.freedesktop.org/git/gstreamer/gstreamer Detailed report: https://oss-fuzz.com/testcase?key=5822394796081152 Project: gstreamer Fuzzer: libFuzzergstreamergst-discoverer Fuzz target binary: gst-discoverer Job Type: libfuzzerasangstreamer Platform Id: linux Crash Type:...