Fix handling of `gap_previous` (#4696) #2157

Job	Run time
Linux [UBSAN] [lmdb \| clang]	38m 59s
macOS [UBSAN] [lmdb \| clang]	32m 25s
Linux [ASAN] [lmdb \| clang]	39m 8s
macOS [ASAN] [lmdb \| clang]	30m 59s
Linux [ASAN_INT] [lmdb \| clang] (Errors Ignored)	40m 31s
macOS [TSAN] [lmdb \| clang]	31m 46s
Linux [TSAN] [lmdb \| clang]	38m 52s
macOS [UBSAN] [rocksdb \| clang]	41m 21s
Linux [LEAK] [lmdb \| clang] (Errors Ignored)	39m 45s
macOS [ASAN] [rocksdb \| clang]	41m 53s
Linux [UBSAN] [rocksdb \| clang]	51m 46s
macOS [TSAN] [rocksdb \| clang]	51m 17s
Linux [ASAN] [rocksdb \| clang]	55m 53s
Linux [ASAN_INT] [rocksdb \| clang] (Errors Ignored)	56m 44s
Linux [LEAK] [rocksdb \| clang] (Errors Ignored)	56m 2s
	10h 47m 21s

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