Incorrect result for string with mixed styles

[erychagov]

Platform: iOS Version: 1.2.3 Example: "~~_**Test**_~~"

How it looks here: ~~Test~~

How it looks after SwiftyMarkdown: ~~Test~~

NSAttributedString has next styles:

Test{
    NSColor = "<UIDynamicSystemColor: 0x7b1000083180; name = labelColor>";
    NSFont = "<UICTFont: 0x7b540056cc00> font-family: \"Times New Roman\"; font-weight: normal; font-style: normal; font-size: 17.00pt";
    NSParagraphStyle = "Alignment 4, LineSpacing 0, ParagraphSpacing 0, ParagraphSpacingBefore 0, HeadIndent 0, TailIndent 0, FirstLineHeadIndent 0, LineHeight 0/0, LineHeightMultiple 0, LineBreakMode 0, Tabs (\n    28L,\n    56L,\n    84L,\n    112L,\n    140L,\n    168L,\n    196L,\n    224L,\n    252L,\n    280L,\n    308L,\n    336L\n), DefaultTabInterval 0, Blocks (\n), Lists (\n), BaseWritingDirection -1, HyphenationFactor 0, TighteningForTruncation NO, HeaderLevel 0 LineBreakStrategy 0";
    NSStrikethrough = 1;
}

I guess the problem is here. The code replaces the previous font style. The strikethroug is the latest what's why we always gets NSAttributedString with NSStrikethrough style.