Handle crashed mirai workers #62

Job	Run time
windows-latest (devel)	6m 31s
windows-latest (release)	6m 35s
windows-latest (oldrel)	6m 33s
macOS-latest (devel)	4m 24s
macOS-latest (release)	3m 4s
macOS-latest (oldrel)	3m 48s
ubuntu-latest (devel)	2m 29s
ubuntu-latest (devel) mirai & nanonext devel	4m 33s
ubuntu-latest (release)	2m 44s
ubuntu-latest (oldrel)	2m 35s
ubuntu-latest (3.6)	2m 26s
	45m 42s

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