This fixes an arithmetic overflow crash on iOS 17 caused by the fallback
lock.
In iOS 17, Swift Mutexes are not available, so we have a fallback class
for NdbUseLock that does not make use of them. This allows some thread
safety for iOS 17 users, but unfortunately not as much as iOS 18+ users.
This attempts to fix those remaining race conditions and subsequent
crashes by using `NSLock` in the fallback class, which is available on
iOS 17.
Closes: https://github.com/damus-io/damus/issues/3512
Changelog-Fixed: Fixed a crash on iOS 17 that would happen on startup
Signed-off-by: Daniel D’Aquino <daniel@daquino.me>
650d4af504