inline code in header with mixed header-ids causes hash entry in toc

[lucascool12]

Describe the bug

The table of contents of a markdown string when mixed header-ids is true contains an incorrect entry that starts with md5- and then a base 64 hash.

To Reproduce

import markdown2
markdown_extensions = {
  "header-ids": {"mixed": True,},
  "toc": {"depth": 1},
}
print(markdown2.markdown("# `bla`\n\nfdsa", extras=markdown_extensions).toc_html)

This prints:

<ul>
  <li><a href="#bla"><code>bla</code></a></li>
  <li><a href="#bla"><code>md5-37f709a7534c73bf50ab64ed70a78d02</code"></a></li>
</ul>

Expected behavior

Only a single <li> entry in the table of contents' <ul>.

Debug info
Version of library being used:
2.5.4

Any extras being used:
See reproducer.

I have reproduced this on e09fb90.
And tried git bisecting this problem and have found 5506a52 to be the first commit were this bug was introduced.