a workaround fix for a gdk_device_get_state bug

This should fix issue #9385 (closed), which results in a crash of Gimp 2.10 when using the newer versions of Wacom device driver with a wacom tablet.

This is a workaround for a gdk_device_get_state bug in gtk2 (See gtk!6045 (closed))

The present PR is an alternative approach to another fix: !934 (closed)

(The initial version of !934 (closed) was more invasive, but the new version is also rather simple.)