Gedit has a transparent background since upgrade to 16.10

Since I upgraded to from 16.04 to 16.10, gedit has strange new "feature": its background is totally transparent.

Where can this come from ?

Notice I'm using Unity and don't have any specific gnome package installed besides what comes by default.
Notice also that in 16.04 I used the Vivacious theme from ravefinity PPA, but I had to go back to Ambiance as Vivacious was broken in 16.10. Maybe it's related.

[EDIT] changing the 'Fonts and Colors' in gedit to any theme other than default (Kate, Solarized, Oblivion, etc..) solves the issue. So there must be a faulty gtksourview file in my home somewhare, but I can't find it...

I had the same problem. After much digging, I found that the file $HOME/.xinputrc was the cause. I just deleted this file with:

rm ~/.xinputrc

The contents of the file are:

# im-config(8) generated on Tue, 18 Aug 2015 16:56:49 -0700
run_im ibus
im-config signature: fef625e6f3691095fd8f4a2f315e85f7  -

After deleting the above file you will need to logout and log back in for changes to take effect (or just reboot).