Bug 135790 ClassCastException in RowData.
ClassCastException is thrown in RowData line 81(IBaseExpression expr = ( IBaseExpression ) valueExpressions.get( index - 1 );).
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/api/script/instance/ICellInstance.java
* Set the column span
	 * 
	 * @param colSpan,
	 *            the column span
	 */
	void setColSpan( int colSpan );
	/**
	 * @return Returns the rowSpan.
	 */
	int getRowSpan( );
	/**
	 * Set the rowspan
	 * 
	 * @param rowSpan,
	 *            the row span
	 */
	void setRowSpan( int rowSpan );
	/**
	 * Get the column number
	 * 
	 * @return the column number
	 */
	int getColumn( );
	
	/**
	 * Get the evaluated expression for this cell
	 * @throws ScriptException 
	 */
	Object getData( ) throws ScriptException;
}