irssi: Attempting free in g_string_append_vprintf

Project: https://github.com/irssi/irssi.git Detailed report: https://clusterfuzz-external.appspot.com/testcase?key=4984573649747968 Project: irssi Fuzzer: libFuzzerirssiirssi-fuzz Fuzz target binary: irssi-fuzz Job Type: libfuzzerasanirssi Platform Id: linux Crash Type: Attempting free Crash...