Don't use output rArea when TableLayouter::getCellArea returns false

...when xCell->isMerged, as happens during CppunitTest_sd_filters_test.
aCellArea will be "empty" (i.e., getMinX()==SAL_MAX_INT32 etc.) and the
aCellRect.Move calculation will overflow for 32-bit long.

Change-Id: I12649234c060edd9f2cab1792cf75335ae22b730

svx/source/table/tablelayouter.cxx

@@ -860,8 +860,8 @@ void TableLayouter::updateCells( Rectangle& rRectangle )
             if( xCell.is() )
             {
                 basegfx::B2IRectangle aCellArea;
-                getCellArea( xCell, aPos, aCellArea );
-
+                if( getCellArea( xCell, aPos, aCellArea ) )
+                {
                     Rectangle aCellRect;
                     aCellRect.Left() = aCellArea.getMinX();
                     aCellRect.Right() = aCellArea.getMaxX();
@@ -872,6 +872,7 @@ void TableLayouter::updateCells( Rectangle& rRectangle )
                 }
             }
         }
+    }
 }