if/elseif fails if there's an HTML comment between the tags

[cossssmin]

Consider the code:

<if condition="1">
  Foo
</if>
<!-- Comment -->
<elseif condition="0">
  Bar
</elseif>

It should display Foo, but instead it displays Foo Bar.

When HTML comment is removed it works as expected.

Originally reported in maizzle/framework#982 by @vkovic.