Is the full biography just a single field? If so, assumming it is called "FullBioField", something like this would only show the link if that field is not empty:
<h2><%# IfEmpty(Eval("FullBioField"), "", "<a href=\"" + GetDocumentUrl() + "\">") %>
<%# Eval("Name") %>
<%# IfEmpty(Eval("FullBioField"), "", "</a>") %>
</h2>
I did not test it but the idea should work. If there are multiple fields that are required to make a "full bio", then you could nest "IfEmpty" calls.