ubsan SwTableBoxFormat is really SwTableLineFormat

 /sw/source/core/doc/tblrwcl.cxx:1937:29: runtime error: downcast of address 0x2b328cff7da8 which does not point to an object of type ´SwTableBoxFormat´
 0x2b328cff7da8: note: object is of type ´SwTableLineFormat´
  00 00 00 00  f0 ea dd 46 32 2b 00 00  b8 80 ff 8c 32 2b 00 00  e8 43 f5 00 90 61 00 00  58 79 65 80
               ^~~~~~~~~~~~~~~~~~~~~~~
               vptr for ´SwTableLineFormat´
     #0 0x2b323c386daf in lcl_CopyLineToDoc(FndLine_ const&, CpyPara*) /sw/source/core/doc/tblrwcl.cxx:1937:29

Change-Id: I16f7b61a3561de3e599818aba538c72c631511ca
Reviewed-on: https://gerrit.libreoffice.org/48282Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

sw/source/core/doc/tblrwcl.cxx

@@ -79,12 +79,12 @@ using namespace com::sun::star::uno;
 struct CpyTabFrame
 {
     union {
-        SwTableBoxFormat *pFrameFormat;     // for CopyCol
-        SwTwips nSize;              // for DelCol
+        SwFrameFormat* pFrameFormat; // for CopyCol
+        SwTwips nSize;               // for DelCol
     } Value;
     SwTableBoxFormat *pNewFrameFormat;
 
-    explicit CpyTabFrame( SwTableBoxFormat* pAktFrameFormat ) : pNewFrameFormat( nullptr )
+    explicit CpyTabFrame(SwFrameFormat* pAktFrameFormat) : pNewFrameFormat( nullptr )
     {   Value.pFrameFormat = pAktFrameFormat; }
 
     bool operator==( const CpyTabFrame& rCpyTabFrame ) const
@@ -279,7 +279,7 @@ static void lcl_CopyCol( FndBox_ & rFndBox, CpyPara *const pCpyPara)
 {
     // Look up the Frame Format in the Frame Format Array
     SwTableBox* pBox = rFndBox.GetBox();
-    CpyTabFrame aFindFrame( static_cast<SwTableBoxFormat*>(pBox->GetFrameFormat()) );
+    CpyTabFrame aFindFrame(pBox->GetFrameFormat());
 
     sal_uInt16 nFndPos;
     if( pCpyPara->nCpyCnt )
@@ -379,7 +379,7 @@ static void lcl_CopyCol( FndBox_ & rFndBox, CpyPara *const pCpyPara)
                     ? rBoxItem.GetTop()
                     : rBoxItem.GetRight() )
             {
-                aFindFrame.Value.pFrameFormat = static_cast<SwTableBoxFormat*>(pBox->GetFrameFormat());
+                aFindFrame.Value.pFrameFormat = pBox->GetFrameFormat();
 
                 SvxBoxItem aNew( rBoxItem );
                 if( 8 > pCpyPara->nDelBorderFlag )