use_build_context_synchronously: Fix not-mounted-or case

[srawlins]

This issue was reported internally. The motivating test case was:

  if (!context.mounted || 1 == 2) {
  } else {
    context /* ref */;
  }

The only way to get into the else branch is if context.mounted is true.

[coveralls]

coverage: 96.73%. remained the same when pulling 5ce85df on ubcs-not-mounted-or into aed089e on main.

[mernen]

I was about to report this issue, as it is a regression in Flutter 3.13. Is it planned for a hotfix release?

[srawlins]

No, I don't believe we will release this in a hotfix.