IOS 中会发生crash的操作

对字典和数组进行下列操作时会产生crash：

对于字典来说：

查询时，key=nil 或者 key=null 时都能正常运行

插入时，，key=nil 或者 key=null 都会crash

对于数组来说

index越界会crash

添加对象为nil时会crash

    NSDictionary *dic = @{@"key":@"value"};
    NSString *value = [dic objectForKey:nil];
    value = [dic objectForKey:[NSNull null]];
    NSMutableDictionary *mutDic = [dic copy];
    value = [mutDic objectForKey:nil];
    value = [mutDic objectForKey:[NSNull null]];
    
    value = [mutDic objectForKey:[NSNull null]];
    
    //    [mutDic setObject:@"123" forKey:nil];crash
    //    [mutDic setObject:nil forKey:@"123"];crash
    //    [mutDic setObject:[NSNull null] forKey:@"key"];crash
    //    [mutDic setObject:@"value" forKey:[NSNull null]];crash
    
//    [mutDic removeObjectForKey:nil]; //crash
//    [mutDic removeObjectForKey:[NSNull null]];//crash
//
    NSArray *arr = @[@(1),@(2),@(3)];
//    value = [arr objectAtIndex:4];//crash
    NSMutableArray *mutArr = [arr mutableCopy];
    
//    [mutArr insertObject:@(5) atIndex:5];//crash
//    [mutArr removeObjectAtIndex:5]; //crash
//    [mutArr replaceObjectAtIndex:5 withObject:@"5"];//crash
//    [mutArr insertObject:nil atIndex:0]; //crash
    
    [mutArr insertObject:[NSNull null] atIndex:0];
    [mutArr replaceObjectAtIndex:0 withObject:[NSNull null]];