There's a SwTxtFrame inside a table, and OptCalc() is called on it which
calls pUpper->Calc(), which reformats rows the table and ends up calling
SwTxtFrm::_AdjustFollow() on some SwTxtFrame that has the first one as
follow.  Use the new ForbidDelete() hack to prevent immediate disaster.

Change-Id: I091704ce6cde15e322986b8f2ecefb5a518f0d8c