cid#1419773: Uninitialized scalar field

Since https://cgit.freedesktop.org/libreoffice/core/commit/?id=2dd1645d7cd12e8f5d8e950af3d156f8df2fa417

Change-Id: I2077bcf1ca53d5378f2690267f307d3350dd037e
Reviewed-on: https://gerrit.libreoffice.org/43401Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

vcl/source/window/dialog.cxx

@@ -492,6 +492,7 @@ void Dialog::ImplInitSettings()
 
 Dialog::Dialog( WindowType nType )
     : SystemWindow( nType )
+    , mbForceBorderWindow(false)
     , mnInitFlag(InitFlag::Default)
 {
     ImplInitDialogData();