Bug 188843 NPE throws out when preview sample report in xls[1203]
engine/org.eclipse.birt.report.engine.emitter.prototype.excel/src/org/eclipse/birt/report/engine/emitter/excel/StyleEngine.java
{
	private static StyleEngine engine = new StyleEngine( );
	private static int ID = 0;
	private Stack styles = new Stack( );
	private Stack spans = new Stack( );
	private Stack pos = new Stack( );
	private Hashtable style2id = new Hashtable( );
	private Hashtable style2top = new Hashtable();
	
	private ListBuffer dataMap = null;	
	/**
	 *