Don't die on missing fetch #876

Job	Run time
docker-master	1h 34m 15s
test-standalone (master, dev, default)	1m 46s
publish-standalone-dry-run	15s
validate-docker-master	22m 13s
test-amd64	2h 18m 11s
build-js-of-ocaml (master, 4.11.1)	5m 14s
generated-files (master)	1m 2s
standalone-haskell (master)	47m 56s
build-wasm-of-ocaml (master, 4.14.1)	17m 12s
deploy-js-wasm-of-ocaml	44s
docker-check-all	3s
	5h 28m 51s

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