Bug 163018 An error extension will lead the report contain chart can't be opened and can not new a report.
Details: An error extension will lead the report contain chart can't open In org.eclipse.birt.report.tests.model has an error extension. When run the birt use workbenck, the report contain chart can't be opened and it can not new a report.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/metadata/ElementDefn.java
throw new MetaDataException( new String[]{name},
					MetaDataException.DESIGN_EXCEPTION_MISSING_XML_NAME );
		
	}
	/**
	 * Check whether the java class specify a correct class which is defined for
	 * this element definition.
	 * 
	 * @throws MetaDataException
	 *             if there is loading error or instantiating error.
	 */
	private void checkJavaClass( ) throws MetaDataException
	{
		if ( StringUtil.isBlank( javaClass ) )
		{
			throw new MetaDataException( new String[]{name},
					MetaDataException.DESIGN_EXCEPTION_MISSING_JAVA_CLASS );
		}
		try
		{
			Class c = Class.forName( javaClass );
			Class clazz = c;
			while ( clazz.getSuperclass( ) != null )
			{
				if ( clazz == DesignElement.class )
					break;
				clazz = clazz.getSuperclass( );
			}
			if ( clazz != DesignElement.class )