glamor: Fix a compiler warning since the recent OOM fixes.

Signed-off-by: Eric Anholt <eric@anholt.net>
3 jobs for ci-glamor in 4 minutes and 52 seconds (queued for 1 second)
Status Job ID Name Coverage
  Docker Image
passed #201423
debian-testing

00:00:33

 
  Build And Test
passed #201424
autotools-build-and-test

00:04:18

passed #201425
meson-build-and-test

00:01:50