fix(db): Fix a sprout/history tree read panic in Zebra 1.4.0, which o… #316

Job	Run time
Generate crates matrix	14s
Check crates matrix	2s
Build tower-batch-control crate	26s
Build tower-fallback crate	32s
Build zebra-chain crate	1m 57s
Build zebra-consensus crate	7m 42s
Build zebra-network crate	2m 8s
Build zebra-node-services crate	1m 46s
Build zebra-rpc crate	7m 41s
Build zebra-scan crate	1m 11s
Build zebra-script crate	1m 49s
Build zebra-state crate	7m 23s
Build zebra-test crate	48s
Build zebra-utils crate	8m 5s
Build zebrad crate	11m 29s
Open or update issues for building crates individually failures	0s
	53m 13s

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