OSV-2021-1779 Heap-use-after-free in Segment::write

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=42996 Crash type: Heap-use-after-free READ 1 Crash state: Segment::write Doublewrite::writepages Doublewrite::flushtodisk...