OSV-2020-2233 Heap-buffer-overflow in flb_sds_cat_utf8

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=28222 Crash type: Heap-buffer-overflow READ 1 Crash state: flbsdscatutf8 flbmsgpackgelfvalue flbmsgpacktogelf...