unbreak LiveState unsub when references.size === 0

[subtleGradient]

fixes #4830 by ensuring that there is only a single path for evicting stuff, ensuring that maybeResolverSubscription gets called correctly

[captbaritone]

Thank you for this. Great catch. Would you mind adding a test case here: https://github.com/facebook/relay/blob/f4c37a333575341b78979106084068cb6b27e1cf/packages/relay-runtime/store/__tests__/resolvers/ResolverGC-test.js so that we don't regress this again?

[subtleGradient]

@captbaritone added the test.
I couldn't figure out how to get the __generated__ stuff to build,
so I reused an existing fragment name, not sure if that matters or not

manually verified that the test fails before the fix and passes after the fix

[subtleGradient]

bummed this didn't make it into 18.2
What still needs to happen before this can land? @captbaritone

[captbaritone]

Sorry for the poor communication. We are in a code freeze currently so not landing any high risk changes that are not necessary, so I wanted to wait to land this one. I'm out next week, but can try to get this landed when I return.

[facebook-github-bot]

@captbaritone has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.