OSV-2020-141 Heap-use-after-free in pixcmapDestroy

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=22110 Crash type: Heap-use-after-free READ 8 Crash state: pixcmapDestroy colorquantfuzzer.cc pixcmapDestroy...