attempt to insert nil object from objects[0] repro code

@interface SomeClass : NSObject

@property (nonatomic, strong) NSDictionary *someDictionary;

@end

@implementation SomeClass

+ (void)load {
    [self new];
}

- (instancetype)init {
    self = [super init];
    
    if (self) {
        NSLock *lock;
        lock = [NSLock new];
        
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0ul), ^{
            NSLog(@"%@", [NSThread currentThread]);
            while (true) {
                @autoreleasepool {
                    int r = arc4random_uniform(2);
                    if (r % 2 == 0) {
                        self.someDictionary = nil;
                    } else {
                        NSMutableDictionary *mutableDict = [NSMutableDictionary dictionary];
                        for (int i = 0; i < 100; i++) {
                            [mutableDict setObject:@"hi" forKey:[[NSProcessInfo processInfo] globallyUniqueString]];
                        }
                        
                        [lock lock];
                        self.someDictionary = mutableDict;
                        [lock unlock];
                    }
                }
            }
        });
        
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0ul), ^{
            NSLog(@"%@", [NSThread currentThread]);
            while (true) {
                @autoreleasepool {
                    [lock lock];
                    NSDictionary *myDict = self.someDictionary;
                    /* This line will throw the exception:
                     
                     Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSPlaceholderArray initWithObjects:count:]: attempt to insert nil object from objects[0]'
                     */
                    NSArray __unused *keys = myDict.allKeys;
                    [lock unlock];
                }
            }
        });
    }
    
    return self;
}

@end