Bug 178519 Problems in multi-rows header
Please see the attachments.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/layout/pdf/cache/TableAreaLayout.java
if(cell.getRowSpan()==1)
				{
					if(cell instanceof DummyCell)
					{
						cell.setHeight( cell.getHeight( ) - height );
					}
					else
					{
						cell.setHeight( height );
						verticalAlign( cell );
					}
					
				}
				else
				{
					hasDropCell = true;
					if(cell instanceof DummyCell)
					{
						cell.setHeight( cell.getHeight( ) - height );
					}
				}
			}
			
			
			if(dropCells.size( )>0)
			{
				HashSet updatedList = new HashSet();
				Iterator iter = dropCells.iterator( );
				while(iter.hasNext( ))
				{