fdo#83354: Chart is truncated - moved down outside the margins of the object

Handle the case when the content height is unitialized (0).
When content height is 0 it means there is no content (so
we don't need to calculate adjustment) or the content height is
uninitialized which leads to wrong calculated value.

Regression from:
cb19042f

Change-Id: I45570a71f0597847820ce77e8dcec4a5b0c6785d

sw/source/core/layout/fly.cxx

@@ -1732,9 +1732,15 @@ void SwFlyFrm::MakeContentPos( const SwBorderAttrs &rAttrs )
         Point aNewContentPos;
         aNewContentPos = Prt().Pos();
         const SdrTextVertAdjust nAdjust = GetFmt()->GetTextVertAdjust().GetValue();
+
         if( nAdjust != SDRTEXTVERTADJUST_TOP )
         {
-            SwTwips nDiff = (Prt().*fnRect->fnGetHeight)() - CalcContentHeight(&rAttrs, nMinHeight, nUL);
+            const SwTwips nContentHeight = CalcContentHeight(&rAttrs, nMinHeight, nUL);
+            SwTwips nDiff = 0;
+
+            if( nContentHeight != 0)
+                nDiff = (Prt().*fnRect->fnGetHeight)() - nContentHeight;
+
             if( nDiff > 0 )
             {
                 if( nAdjust == SDRTEXTVERTADJUST_CENTER )