Bug#445950: tex-guy.desktop points to an inexistent executable xgdviviewer
Here is the contents of /usr/share/applications/tex-guy.desktop:
Comment=Veiw DVIs produced with TeX and LaTeX
xgdviviewer is not part of tex-guy nor of any Debian package. There is a
xgdvi executable in xgdvi though, the source package of which is
tex-guy, that does not have a .desktop file.