我有一个应用程序，用户报告它在随机时间崩溃。所有崩溃都有相同的堆栈
0 CoreFoundation TAGPBIvarClearUInt32 (in SPONTAN) + 11
1 libobjc.A.dylib _mh_execute_header (in SPONTAN) + 15567
2 CoreFoundation TAGPBIvarClearSFixed64 (in SPONTAN) + 13
3 Foundation -[AdvancedPriceViewController newAP:] (in SPONTAN) (AdvancedPriceViewController.m:68) + 110325
4 SPONTAN +[TrStart isJSONTrStart:] (in SPONTAN) + 77
5 SPONTAN __65-[MintRequestWorker processPreviousLoggedRequestsAsyncWithBlock:]_block_invoke_2 (in SPONTAN) + 397
6 SPONTAN __58-[FileRepository readLoggedExceptionsWithCompletionBlock:]_block_invoke (in SPONTAN) + 281
7 libdispatch.dylib _mh_execute_header (in SPONTAN) + 6195
8 libdispatch.dylib -[FirstViewController viewDidLoad] (in SPONTAN) (FirstViewController.m:56) + 84257
9 libdispatch.dylib -[FirstViewController viewDidAppear:] (in SPONTAN) (FirstViewController.m:80) + 84769
10 libsystem_pthread.dylib _mh_execute_header (in SPONTAN) + 3027
11 libsystem_pthread.dylib _mh_execute_header (in SPONTAN) + 2712
这可能看起来不错，但是当我查看级别 3、8 和 9 时，代码不再有意义。
3 Foundation -[AdvancedPriceViewController newAP:] (in SPONTAN) (AdvancedPriceViewController.m:68) + 110325
Line 68: NSMutableArray *arrayOfIndexPaths = [[NSMutableArray alloc] init];
8 libdispatch.dylib -[FirstViewController viewDidLoad] (in SPONTAN) (FirstViewController.m:56) + 84257
Line 56: [[SelectCity titleLabel] setFont:[UIFont fontWithName:@"Avenir" size:15]];
9 libdispatch.dylib -[FirstViewController viewDidAppear:] (in SPONTAN) (FirstViewController.m:80) + 84769
Line 80: NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
错误是 NSRangeException
*** -[__NSCFConstantString substringToIndex:]: Index 2147483647 out of bounds; string length 0
谁能告诉我这里发生了什么？