Bug 165278 this.getDisplayContent()="" in script of text will destroy preview[0801]
Description: this.getDisplayContent()="" in script of text will destroy preview Build number:2.1.2.v20061120 and 2.2.0.v20061117 Steps to reproduce: 1. Insert a text item, select it and switch to script editor 2. Input this.getDisplayContent()="" and preview Expected result: Error message about the incorrect script. Actual result: In 2.1.2, I saw HTTP Status 500 - type Exception report message description The server encountered an internal error () that prevented it from fulfilling this request. In 2.2.0, I saw error dialog with java.lang.ClassCastException.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/executor/ExecutionContext.java
{
	
	private static Logger log = Logger.getLogger( ExecutionContext.class
			.getName( ) );
	public static final String PROPERTYSEPARATOR = ";";
	
	
	private IReportEngine engine;
	/**
	 * task ID string
	 */
	private String taskIDString;
	/**
	 * execution mode, in this mode, the render operation should be executed.
	 */
	private boolean presentationMode = false;
	/**