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
/**
	 * get a string formatter object
	 * 
	 * @param value
	 *            string format
	 * @return formatter object
	 */
	public StringFormatter getStringFormatter( String value )
	{
		StringFormatter fmt = (StringFormatter) stringFormatters.get( value );
		if ( fmt == null )
		{
			fmt = new StringFormatter( value, ULocale.forLocale(locale) );
			stringFormatters.put( value, fmt );
		}
		return fmt;
	}
	/**
	 * get a number formatter object
	 * 
	 * @param value
	 *            number format
	 * @return formatter object
	 */
	public NumberFormatter getNumberFormatter( String value )
	{
		NumberFormatter fmt = (NumberFormatter) numberFormatters.get( value );
		if ( fmt == null )
		{
			fmt = new NumberFormatter( value, ULocale.forLocale(locale) );