tdf#122722 sw: fix hidden text crash in SwTextFrame::GetCurWord()

A frame that is fully hidden does not have a SwParaPortion,
see SwTextFrame::Format() early return.

(regression from 9bda4a67565817f0a26f48c4a4b9723894a385f5)

Change-Id: I6b06824e53cef7218b60f60fced8f863adad8b62
Reviewed-on: https://gerrit.libreoffice.org/66385
Tested-by: Jenkins
Reviewed-by: Michael Stahl <Michael.Stahl@cib.de>
diff --git a/sw/source/core/txtnode/txtedt.cxx b/sw/source/core/txtnode/txtedt.cxx
index 929faa9..11a29bd 100644
--- a/sw/source/core/txtnode/txtedt.cxx
+++ b/sw/source/core/txtnode/txtedt.cxx
@@ -703,7 +703,7 @@
    OUString const& rText(GetText());
    assert(sal_Int32(nPos) <= rText.getLength()); // invalid index

    if (rText.isEmpty())
    if (rText.isEmpty() || IsHiddenNow())
        return OUString();

    assert(g_pBreakIt && g_pBreakIt->GetBreakIter().is());