EXC_BAD_ACCESS: autoLockTimerDate

[sashei]

There are several instances in which accessing autoLockTimerDate has failed. This ticket will track making sure that all accesses to the current autoLockTimerDate are "safe".

https://sentry.prod.mozaws.net/operations/lockbox-ios/issues/5411384/

EXC_BAD_ACCESS: autoLockTimerDate > spatch_source >
Attempted to dereference garbage pointer 0x9567bec8.
  ?, in <redacted>
  ?, in <redacted>
  ?, in <redacted>
  File "RxSwift/ObservableType+Extensions.swift", line 65, in closure #1 in ObservableType.subscribe(onNext:onError:onCompleted:onDisposed:)
  File "<compiler-generated>", in partial apply for closure #1 in ObservableType.subscribe(onNext:onError:onCompleted:onDisposed:)
...
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