Resolves: tdf#122059 don't crash with no parent for tabpage

Change-Id: Id27609a86558094e6b53c763aebe77c97cc11672
Reviewed-on: https://gerrit.libreoffice.org/65147
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>
diff --git a/vcl/source/window/tabpage.cxx b/vcl/source/window/tabpage.cxx
index c9bff32..ad3c12e 100644
--- a/vcl/source/window/tabpage.cxx
+++ b/vcl/source/window/tabpage.cxx
@@ -61,7 +61,7 @@ void TabPage::ImplInitSettings()
        SetParentClipMode();
        SetPaintTransparent( false );

        if ( IsControlBackground() )
        if (IsControlBackground() || !pParent)
            SetBackground( GetControlBackground() );
        else
            SetBackground( pParent->GetBackground() );