Fix crash on XkbSetMap

Some devices may not have keyboard information.

Fixes #574

(cherry picked from commit 8469bfea)
3 jobs for server-1.20-branch in 5 minutes and 33 seconds
Status Job ID Name Coverage
  Docker Image
passed #739593
debian-testing

00:00:31

 
  Build And Test
passed #739594
autotools-build-and-test

00:05:01

passed #739595
meson-build-and-test

00:01:33