Fixed a crash from when NSAttributedStringMarkdownLink was typecast as NSValue

I found a crash in my application today coming from `- (void)recurseOnString:(NSString *)string withFont:(UIFont *)font` and it was coming from line 230, which is `NSRange range = [rangeValue rangeValue];`

I am not exactly sure when this method is called, but it seems that this method thinks `recursiveParser.links` will hold an array of `NSValue`'s, but in my testing it contains an array of `NSAttributedStringMarkdownLink`

Could you let me know if this fix is on the right track or just a band-aid, which doesn't really fix the issue. Thanks!