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 Name Job ID Coverage
  Docker Image
passed debian-testing #739593

00:00:31

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

00:05:01

passed meson-build-and-test #739595

00:01:33