wayland/tablet-tool: Check for non-NULL surface resource
A MetaWaylandSurface object can outlive the corresponding wl_surface object since !1880 (merged) .
Closes: #3320 (closed)
Edited by Robert Mader
A MetaWaylandSurface object can outlive the corresponding wl_surface object since !1880 (merged) .
Closes: #3320 (closed)