Yeah, I was just going to post that you may want to make it conditional:
Code:
<if condition="$post[field7]">$post[fieldX]<else />$post[musername]</if>
Also, by doing this, you're stripping the name of all of its markup. It may not be the best idea.
Edit: You can retain the usergroup's html markup if you edit it the functions.php file, but is there any other way to do it without file edits?