Add back initialization of ScNavigatorSettings::maExpandedVec

...lost with 2ea92be9 "convert SC_CONVERT
constants to scoped enum".  And indeed, e.g., opening the document from
<https://bugs.documentfoundation.org/show_bug.cgi?id=114932#c2> through steps 1
and 2 in a UBSan build reports a use of an uninitialized (bad-valued) bool in
ScNavigatorSettings::IsExpanded.

Change-Id: If0dfadc6bd8033e61e334f59b3028ab005a892cd
Reviewed-on: https://gerrit.libreoffice.org/47767Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
(cherry picked from commit fbec01b7)
Reviewed-on: https://gerrit.libreoffice.org/47785Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

sc/source/ui/navipi/navipi.cxx

@@ -435,6 +435,7 @@ ScNavigatorSettings::ScNavigatorSettings()
     : mnRootSelected(ScContentId::ROOT)
     , mnChildSelected(SC_CONTENT_NOCHILD)
 {
+    maExpandedVec.fill(false);
 }
 
 SFX_IMPL_CHILDWINDOWCONTEXT( ScNavigatorDialogWrapper, SID_NAVIGATOR )