Merge pull request #8587 from zhiqiangxu/add_nil_check #1

Job	Run time
cross compilation	27m 9s
lint code	41s
check commits	0s
check pinned dependencies (google.golang.org/grpc v1.56.3)	4s
check pinned dependencies (github.com/golang/protobuf v1.5.3)	8s
run macOS itest	1h 58m 8s
check release notes updated	5s
RPC and mobile compilation check	3m 19s
sample configuration check	1m 36s
Sqlc check	40s
run ubuntu itests (btcd, backend=btcd)	42m 16s
run unit tests (btcd unit-cover)	17m 9s
run windows itest	56m 44s
run ubuntu itests (bitcoind, backend=bitcoind)	53m 1s
run unit tests (unit tags="kvdb_etcd")	18m 44s
run ubuntu itests (bitcoind-notxindex, backend="bitcoind notxindex")	52m 57s
run unit tests (unit tags="kvdb_postgres")	17m 18s
run unit tests (unit tags="kvdb_sqlite")	16m 34s
run ubuntu itests (bitcoind-rpcpolling, backend="bitcoind rpcpolling")	53m 9s
run unit tests (btcd unit-race)	34m 45s
run ubuntu itests (bitcoind-etcd, backend=bitcoind dbbackend=etcd)	1h 10m 49s
run unit tests (unit-module)	1m 59s
run ubuntu itests (bitcoind-postgres, backend=bitcoind dbbackend=postgres)	1h 23m 41s
run ubuntu itests (bitcoind-sqlite, backend=bitcoind dbbackend=sqlite)	56m 1s
run ubuntu itests (bitcoind-postgres-nativesql, backend=bitcoind dbbackend=postgres nativesql=true)	1h 24m 50s
run ubuntu itests (bitcoind-sqlite-nativesql, backend=bitcoind dbbackend=sqlite nativesql=true)	56m 9s
run ubuntu itests (neutrino, backend=neutrino)	51m 8s
	15h 19m 4s

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