Resolves: tdf#130541 null-deref on detaching already-detached page

Change-Id: Ib48ab91232b8ff624a1387ab82701938eef58ded
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/88380
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
diff --git a/extensions/source/propctrlr/browserpage.cxx b/extensions/source/propctrlr/browserpage.cxx
index edb6b08..5502418 100644
--- a/extensions/source/propctrlr/browserpage.cxx
+++ b/extensions/source/propctrlr/browserpage.cxx
@@ -32,7 +32,9 @@ namespace pcr

    OBrowserPage::~OBrowserPage()
    {
        m_pParent->move(m_xContainer.get(), nullptr);
        if (m_pParent)
            detach();
        assert(!m_pParent);
    }
} // namespace pcr