tdf#125751 sw: don't start recursive layout in SwTextFrame::EmptyHeight()

Not sure if this has anything to do with the bug, but i noticed it while
debugging...

This is the only place that calls GetCurrFrame() *during* formatting,
so make sure we don't do stupid recursive things.

(regression from 56b2cf0c10d9caa01ebae1d80465e342d046a85c)

Change-Id: Icd05f8d634bc9de4d5d16824d30075397e6c9960
Reviewed-on: https://gerrit.libreoffice.org/74750
Tested-by: Jenkins
Reviewed-by: Michael Stahl <Michael.Stahl@cib.de>
(cherry picked from commit 7a05458d39da2f4755cb6e190dce338198655137)
Reviewed-on: https://gerrit.libreoffice.org/74787
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>
diff --git a/sw/source/core/text/porrst.cxx b/sw/source/core/text/porrst.cxx
index 07dbf9d..53bb745 100644
--- a/sw/source/core/text/porrst.cxx
+++ b/sw/source/core/text/porrst.cxx
@@ -211,7 +211,8 @@ SwTwips SwTextFrame::EmptyHeight() const
        SwViewShell *pSh = getRootFrame()->GetCurrShell();
        if ( dynamic_cast<const SwCursorShell*>( pSh ) !=  nullptr ) {
            SwCursorShell *pCrSh = static_cast<SwCursorShell*>(pSh);
            SwContentFrame *pCurrFrame=pCrSh->GetCurrFrame();
            // this is called during formatting so avoid recursive layout
            SwContentFrame const*const pCurrFrame = pCrSh->GetCurrFrame(false);
            if (pCurrFrame==static_cast<SwContentFrame const *>(this)) {
                // do nothing
            } else {