Crash when enabling iCloud sync in non-entitled builds

[tymrtn]

Summary

Enabling iCloud sync can crash Flycut in builds that do not have valid iCloud entitlements (for example local unsigned builds used for debugging).

Affected area

• iCloud sync startup path (MJCloudKitUserDefaultsSync)

Steps to reproduce

1. Launch Flycut in a build without iCloud entitlements.
2. Enable iCloud Clippings Sync in Preferences.
3. Save/close preferences.

Alternative repro via defaults:

defaults write com.generalarcade.flycut syncClippingsViaICloud -bool true
defaults write com.generalarcade.flycut savePreference -int 2

Then launch Flycut.

Actual behavior

Flycut terminates due to CloudKit startup path reaching invalid container/entitlement state.
Observed crash signatures include:

• CKException: containerIdentifier can not be nil
• CloudKit _os_crash (EXC_BREAKPOINT/SIGTRAP) in enable path

Expected behavior

If iCloud container configuration/entitlements are unavailable, Flycut should not crash. It should safely skip CloudKit enablement.

Proposed fix

Add defensive guards in MJCloudKitUserDefaultsSync:

• Verify effective container identifier before enabling.
• Verify process has iCloud container entitlement before CloudKit calls.
• Wrap container creation in exception-safe checks and bail out cleanly.

Notes

This does not change normal signed/entitled behavior. It only prevents hard crashes when the environment cannot support CloudKit.

[GwynethLlewelyn]

Nice catch! Having only used 'entitled builds', this was something I never noticed — Flycut is the most rock-solid applet I've ever used. The last build was in 2020 (thankfully, released as an Universal Binary... phew!), so I hope @TermiT approves your PR, which means getting a new update (woo-hoo!), possibly compiled with more recent, faster and secured libraries!...