App suddenly crashes on iOS 9.3 after update at: [NSMetadataItem valueForAttribute:]

A week ago I released an update to my iOS app and suddenly my app crashes at [NSMetadataItem valueForAttribute:] for users still running iOS 9.3.x.


I did not touch any iCloud related code in my app and changed a completely different part for the update, so I'm puzzled why the app is crashing all of a sudden (no such crashes were reported in previous versions).


The app only seems to crash on iOS 9.3.x.


The other thing that changed is that I now build against the iOS 12.1 SDK. Could there be a bug in the iOS SDK (or iOS 9) that could cause this bug to surface?


Below is the relevant part of the crash log.


I'm grateful for any hints or suggestions.


Hardware Model:      iPad3,1
Code Type:           ARM (Native)
Parent Process:      launchd [1]


OS Version:          iOS 9.3.5 (13G36)
Report Version:      105


Exception Type:  EXC_BAD_ACCESS (SIGSEGV)
Exception Subtype: KERN_INVALID_ADDRESS at 0x00000010
Triggered by Thread:  0


Global Trace Buffer (reverse chronological seconds):
7.532444     CFNetwork                 0x000000002296f87d TCP Conn 0x156325c0 complete. fd: 4, err: 0
7.534582     CFNetwork                 0x0000000022970977 TCP Conn 0x156325c0 event 1. err: 0


Thread 0 name:
Thread 0 Crashed:
0   libswiftCore.dylib             0x0076e52e 0x50a000 + 2508078
1   Foundation                     0x22babfac -[NSBundle classNamed:] + 80 (NSBundle.m:1200)
2   CloudDocs                     0x305451d6 __34+[BRContainerCache containerCache]_block_invoke + 58 (BRContainer.m:2254)
3   libdispatch.dylib             0x21f5d80e _dispatch_client_callout + 22 (init.c:819)
4   libdispatch.dylib             0x21f6f172 dispatch_once_f$VARIANT$mp + 62 (once.c:60)
5   CloudDocs                     0x30545198 +[BRContainerCache containerCache] + 60 (once.h:68)
6   CloudDocs                     0x30539daa -[NSURL(BRAdditions) br_cloudDocsContainer] + 58 (NSURL+BRAdditions.m:398)
7   CloudDocs                     0x3052ffe0 __25+[BRQueryItem initialize]_block_invoke_24 + 40 (BRQueryItem.m:224)
8   Foundation                     0x22bb8a80 -[NSMetadataItem valueForAttribute:] + 160 (NSMetadata.m:172)