Fix: panics occur when the timestamp file does not exist in a scheme … #571

Job	Run time
docker-build	1m 20s
docker-build	1m 20s
lint	1m 25s
lint	1m 25s
test	7m 48s
test	8m 53s
build (linux, amd64)	1m 11s
build (linux, amd64)	1m 11s
build (linux, 386)	1m 2s
build (linux, 386)	1m 2s
build (linux, arm)	1m 14s
build (linux, arm)	1m 14s
build (linux, arm64)	1m 19s
build (linux, arm64)	1m 19s
build (darwin, amd64)	1m 19s
build (darwin, amd64)	1m 19s
build (darwin, arm64)	55s
build (darwin, arm64)	55s
build (windows, amd64)	55s
build (windows, amd64)	55s
build (windows, 386)	54s
build (windows, 386)	54s
build (windows, arm)	54s
build (windows, arm)	54s
build (windows, arm64)	54s
build (windows, arm64)	54s
analyze	3m 40s
analyze	3m 40s
integration-test-serverside (f0023141ec429d912e329665f937d05b178a3fee)	4m 6s
integration-test-serverside (f0023141ec429d912e329665f937d05b178a3fee)	4m 6s
integration-test-clientside (v0.13.2)	2m 56s
integration-test-clientside (v0.13.2)	2m 56s
	1h 4m 49s

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