[gnome-control-center/gnome-3-32] display: Fix crash if a monitor has no preferred mode

[Benjamin Berg <bberg src gnome org>]

commit 4d64299561558ee9b23f1259c8491014ea62432b
Author: Benjamin Berg <bberg redhat com>
Date:   Fri Apr 26 18:39:03 2019 +0200

    display: Fix crash if a monitor has no preferred mode
    
    When a monitor has no current mode set and also no preferred mode we ran
    into a crash. Simply select the first mode we can find as a further
    fallback.
    
    (cherry picked from commit f75c3a8471d24bc8c4402c60cedcb0cdfcf476e3)

 panels/display/cc-display-settings.c | 6 ++++++
 1 file changed, 6 insertions(+)
---
diff --git a/panels/display/cc-display-settings.c b/panels/display/cc-display-settings.c
index 562670298..6ab1ac832 100644
--- a/panels/display/cc-display-settings.c
+++ b/panels/display/cc-display-settings.c
@@ -269,6 +269,12 @@ cc_display_settings_rebuild_ui (CcDisplaySettings *self)
   current_mode = cc_display_monitor_get_mode (self->selected_output);
   if (current_mode == NULL)
     current_mode = cc_display_monitor_get_preferred_mode (self->selected_output);
+  if (current_mode == NULL) {
+    modes = cc_display_monitor_get_modes (self->selected_output);
+    /* Lets assume that a monitor always has at least one mode. */
+    g_assert (modes);
+    current_mode = CC_DISPLAY_MODE (modes->data);
+  }
 
   if (should_show_rotation (self))
     {