Don't ask "open (embedded) or save" if we have no part to embed anyway.
This fixes the double-question (open or save + open with ark or save) when clicking on a tar.gz in <a href="http://www.exiv2.org/archive.html">http://www.exiv2.org/archive.html</a>;

I keep wondering about merging those two into a single "open embedded / open in app / save" dialog...