frames: Allow for unknown mouse buttons

frames: Allow for unknown mouse buttons

Commit 47131b1d ("frames: Handle touch events") introduced an assert to
make sure that all mouse button actions are handled in mutter.

However, mice can have a more than 5 buttons, so simply ignore the
"other" actions instead of aborting.

(cherry picked from commit 473bf38753221dc0002fae309d2f3f217e96c5f5)

Bug: https://gitlab.gnome.org/GNOME/mutter/issues/160
Bug-Debian: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=899181
Origin: upstream, 3.28.3, commit:1a3f9a33234f8406ffcaa150df542b73715910f4

Gbp-Pq: Name frames-Allow-for-unknown-mouse-buttons.patch