Handle monitors that have no manufacturer/model names

As in GH actions CI.

Author: Cimbali

.github/workflows/draft_release.yml

@@ -52,9 +52,7 @@ jobs:
     - name: Test starting pympress and quitting from the command line
       if: always()
       run: |
-        pympress &
         pympress --quit
-        wait %1
 
     - name: Check the log has been created from the previous step
       if: always()

pympress/ui.py

@@ -2004,9 +2004,8 @@ def lookup_monitors(display, *windows):
                                      the best monitor areas for primary and non-primary monitors
         """
         # Helpful for debugging
-        name = [mon.get_manufacturer() + ' ' + mon.get_model() for mon in (
-            display.get_monitor(n) for n in range(display.get_n_monitors())
-        )]
+        name = ['{} {}'.format(mon.get_manufacturer() or 'Unknown manufacturer', mon.get_model() or 'Unknown model')
+                for mon in (display.get_monitor(n) for n in range(display.get_n_monitors()))]
 
         all_geom = [ScreenArea(display.get_monitor(n).get_geometry(), name[n]) for n in range(display.get_n_monitors())]
         # Remove duplicate monitors (“mirrored”)