I started seeing a large number of these crashes starting on June 8. Same backtrace. So far seeing only on iOS 14.4.2.

I'm seeing the same crash in iOS 14.4.2, 14.4, and 14.3 in an iPad app. First started seeing them on June 8. NSInvalidArgumentException: -[__NSCFNumber compare:]: nil argument 0 CoreFoundation ___exceptionPreprocess 1 libobjc.A.dylib _objc_exception_throw 2 CoreFoundation __CFThrowFormattedException 3 CoreFoundation -[__NSCFNumber compare:].cold.1 4 CoreFoundation -[__NSCFNumber compare:] 5 CoreFoundation -[__NSCFNumber isEqualToNumber:] 6 CoreText +[FontAssetDownloadManager filterIncompatibleAsset:] 7 CoreText +[FontAssetDownloadManager availableMobileAssetsWithOptions:error:] 8 CoreText +[FontAssetDownloadManager availableMobileAssetsWithOptions:manager:error:] 9 CoreText -[FontAssetDownloadManager mobileAssetsForUnmatched:] 10 CoreText -[FontAssetDownloadManager downloadFontAssets] 11 CoreText ___CTFontDescriptorMatchFontDescriptorsWithProgressHandler_block_invoke 12 libdispatch.dylib __dispatch_call_block_and_release 13 libdispatch.dylib __dispatch_client_callout 14 libdispatch.dylib __dispatch_lane_serial_drain$VARIANT$mp 15 libdispatch.dylib __dispatch_lane_invoke$VARIANT$mp 16 libdispatch.dylib __dispatch_workloop_worker_thread 17 libsystem_pthread.dylib __pthread_wqthread 18 libsystem_pthread.dylib _start_wqthread

I have added steps to reproduce and a detailed explanation of the crash to FB9147434. At this time, the fix seems to be to update to iOS 14.5 or above.

The iOS 15 release notes seem to indicate takeUnretainedValue shouldn't be necessary here anymore: cgImageRepresentation() and previewCGImageRepresentation() now return CGImage? instead of Unmanaged? in Swift. (44734827)