fdo#42147: fix crash

it is not valid to use (type & ND_TEXTNODE) before casting to SwTxtNode,
type of SwCntntNode has the ND_TEXTNODE bit as well, but SwCntntNode is not
derived from SwTxtNode.

sw/source/core/crsr/callnk.cxx

@@ -70,7 +70,7 @@ SwCallLink::SwCallLink( SwCrsrShell & rSh )
     nNdTyp = rNd.GetNodeType();
     bHasSelection = ( *pCrsr->GetPoint() != *pCrsr->GetMark() );
 
-    if( ND_TEXTNODE & nNdTyp )
+    if( rNd.IsTxtNode() )
         nLeftFrmPos = SwCallLink::getLayoutFrm( rShell.GetLayout(), (SwTxtNode&)rNd, nCntnt,
                                             !rShell.ActionPend() );
     else

sw/source/core/crsr/crsrsh.cxx

@@ -223,7 +223,7 @@ void SwCrsrShell::StartAction()
         nAktCntnt = pCurCrsr->GetPoint()->nContent.GetIndex();
         nAktNdTyp = rNd.GetNodeType();
         bAktSelection = *pCurCrsr->GetPoint() != *pCurCrsr->GetMark();
-        if( ND_TEXTNODE & nAktNdTyp )
+        if( rNd.IsTxtNode() )
             nLeftFrmPos = SwCallLink::getLayoutFrm( GetLayout(), (SwTxtNode&)rNd, nAktCntnt, sal_True );
         else
             nLeftFrmPos = 0;