Freeze break request #2 for mutter

[Jonas Ådahl <jadahl gmail com>]

Hi again,

I have another freeze break request for mutter. This time it's a crash
fix for a race with a very safe patch fixing it (just a NULL check). It
happens mostly if you press the left mouse button directly after the
right mouse button on where right mouse button maps a popup Wayland.

Even with the release around the corner, I think this one is safe
enough, and fixes a crash that could easily happen, as long as you use a
real mouse device.

This is the bug in question:
https://bugzilla.gnome.org/show_bug.cgi?id=771495


Jonas