steps to reproduce
1. configure emacs to use pgtk
2. emacs -Q
3. C-z or M-x iconify-frame
4. Restore emacs by clicking on its icon
Emacs does not display characters any more.
I believe this bug is similar to bug#42655 except this time it is for pgtk and not lucid.
I believe I have fixed this problem and will attach a patch in the next mail, but the thing is I have no idea how I fixed it so please check for any unintended consequences.
Thanks