Please comment (add #) or remove
# application/octet-stream=gedit.desktop;
in your
~/.local/share/applications/mimeapps.list
That's works for me.
Firefox Opening Pdfs in Gedit
Please comment (add #) or remove
# application/octet-stream=gedit.desktop;
in your
~/.local/share/applications/mimeapps.list
That's works for me.