`<outlook not="unexpected value">` stops the conditional rendering

[cossssmin]

Originally created in maizzle/framework by @mconnell

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Discovered through an accident in the documentation..

The documentation for <outlook> (https://maizzle.com/docs/tags#outlook) lists an optional not attribute. Thinking that the <outlook> tag was emitting <!--[if mso|ie]> the thought was to apply the following:

<outlook not="ie">
  Some markup
</outlook>

Ignoring the documentation was slightly wrong, the potential bug/issue is that when an unexpected value is passed to the not attribute, the MSO conditional isn't rendered at all. Instead we just get:

  Some markup

I think the desired behaviour should be for the tag to ignore the bad value and still generate the conditional e.g.

<!--[if mso|ie]>
  Some markup
<![endif]-->