Resolves: tdf#130164 background/border dialog should be modal

Change-Id: I763cc054b23d4f72e1dec175861f3062d6bda6fe
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/87346
Tested-by: Jenkins
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>
diff --git a/cui/uiconfig/ui/borderbackgrounddialog.ui b/cui/uiconfig/ui/borderbackgrounddialog.ui
index 3744373..1471696 100644
--- a/cui/uiconfig/ui/borderbackgrounddialog.ui
+++ b/cui/uiconfig/ui/borderbackgrounddialog.ui
@@ -1,5 +1,5 @@
<?xml version="1.0" encoding="UTF-8"?>
<!-- Generated with glade 3.20.0 -->
<!-- Generated with glade 3.22.1 -->
<interface domain="cui">
  <requires lib="gtk+" version="3.18"/>
  <object class="GtkDialog" id="BorderBackgroundDialog">
@@ -7,7 +7,11 @@
    <property name="border_width">6</property>
    <property name="title" translatable="yes" context="borderbackgrounddialog|BorderBackgroundDialog">Border / Background</property>
    <property name="resizable">False</property>
    <property name="modal">True</property>
    <property name="type_hint">dialog</property>
    <child>
      <placeholder/>
    </child>
    <child internal-child="vbox">
      <object class="GtkBox" id="dialog-vbox1">
        <property name="can_focus">False</property>