[gnome-nibbles/arnaudb/wip/gtk4: 48/62] Other backportable fix.

[Arnaud B. <arnaudb src gnome org>]

commit d0df7c8415c0015574792bdeb28c7837f5030ec4
Author: Arnaud Bonatti <arnaud bonatti gmail com>
Date:   Tue Jun 16 11:54:30 2020 +0200

    Other backportable fix.

 src/preferences-dialog.vala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/preferences-dialog.vala b/src/preferences-dialog.vala
index bbac994..3ee09e8 100644
--- a/src/preferences-dialog.vala
+++ b/src/preferences-dialog.vala
@@ -186,7 +186,7 @@ private class PreferencesDialog : Window
              || keyval == worm_settings [i].get_int ("key-right"))
             {
                 var dialog = new MessageDialog (this,
-                                                DialogFlags.DESTROY_WITH_PARENT,
+                                                DialogFlags.MODAL,
                                                 MessageType.WARNING,
                                                 ButtonsType.CANCEL,
                                                 /* Translators: label of a MessageDialog that appears when 
one tries to assign an already assigned key */