Broken schema 'org.gtk.Settings.FileChooser'

For the past few weeks (after a distribution upgrade), about every program with a graphical user interfaces crashes at some point with the same error:

GLib-GIO-ERROR **: Settings schema 'org.gtk.Settings.FileChooser' does not contain a key named 'last-folder-uri'

It happens every time a file open dialog shows up, but also when the network manager asks for a WiFi password. (Which means I can't open files in any gtk application and only connect to open wireless networks.)

/usr/share/glib-2.0/schemas/org.gtk.Settings.FileChooser.gschema.xml does contain <key name='last-folder-uri'

Running glib-compile-schemas doesn't seem to help.

It's not just for one user. If I log in as a guest ('Guest Session'), the same happens.

$ dpkg -s libgtk-3-common | grep Version
Version: 3.4.2-0ubuntu0.3

Contents of /usr/share/glib-2.0/schemas/org.gtk.Settings.FileChooser.gschema.xml:

<https://gist.github.com/f90a230bf6077cbaa967>

A bit late but... just for future reference.

I already met this very same issue, just with a different key: you probably have a double org.gtk.Settings.FileChooser.gschema.xml file installed on your filesystem.

You should remove that file (I just uninstalled the culprit package) to solve the issue. Check this question for further details.