tdf#132210: fix Calc crash when closing spreadsheet file

make the dialog modal
See bt:
https://bugs.documentfoundation.org/attachment.cgi?id=159677

Change-Id: I75719fe241950f13c2e5d65c5d9078193e631ffd
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/92438
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
diff --git a/sc/uiconfig/scalc/ui/movecopysheet.ui b/sc/uiconfig/scalc/ui/movecopysheet.ui
index 1da0b27..a700a77 100644
--- a/sc/uiconfig/scalc/ui/movecopysheet.ui
+++ b/sc/uiconfig/scalc/ui/movecopysheet.ui
@@ -14,6 +14,7 @@
    <property name="can_focus">False</property>
    <property name="border_width">6</property>
    <property name="title" translatable="yes" context="movecopysheet|MoveCopySheetDialog">Move/Copy Sheet</property>
    <property name="modal">True</property>
    <property name="type_hint">dialog</property>
    <child internal-child="vbox">
      <object class="GtkBox" id="dialog-vbox1">