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
* Loads scripts that are stored in an external file. Used to support
	 * include-script. Each script file should be load only once. and the script
	 * in the file must be encoded in UTF-8.
	 * 
	 * @param fileName
	 *            script file name
	 */
	public void loadScript( String fileName )
	{
		ReportDesignHandle reportDesign = this.getDesign( );
		URL url = null;
		if ( reportDesign != null )
		{
			url = reportDesign.findResource( fileName,
					IResourceLocator.LIBRARY );
		}
		if (url == null)
		{
			return;
		}
		
		
		try
		{
			InputStream in = url.openStream( );
			ByteArrayOutputStream out = new ByteArrayOutputStream( );
			byte[] buffer = new byte[1024];
			int size = in.read( buffer );
			while ( size != -1 )
			{