Comment 4 for bug 1310718

I can confirm this bug. It actually broke my dist-upgrade from 12.04 to 14.04. I fixed it manually by deleting the broken script and removing gdm.

I tried to reinstall gdm today but the package is still broken, i. e. the post-install script is broken. Executing it manually with

   bash -x /var/lib/dpkg/info/gdm.postinst

results in:

+ set -e
+ . /usr/share/debconf/confmodule
++ '[' '!' '' ']'
++ PERL_DL_NONLAZY=1
++ export PERL_DL_NONLAZY
++ '[' '' ']'
++ exec /usr/share/debconf/frontend /var/lib/dpkg/info/gdm.postinst
Use of uninitialized value $action in string eq at /usr/share/debconf/frontend line 27.