Logic Error in Texturize Element Stack

[miqrogroove]

Test case:

wptexturize( '<span>hello</code>---</span>' );

Expected result:

<span>hello</code>&#8212;</span>

Actual result:

<span>hello</code>---</span>

This is being caused by a rather obvious logic flaw in the texturize stack, and inadequate unit testing.

[wonderboymusic]

In 28763:

Add unit tests to confirm that --- is properly converted to — by wptexturize() where appropriate.

Props miqrogroove.
Fixes #28483.