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
*/
	void setCanExtend( boolean flag )
	{
		allowExtend = flag;
	}
	/**
	 * Returns whether elements of this class can be extended.
	 * 
	 * @return True if the element can be extended, false if not.
	 */
	public boolean canExtend( )
	{
		return allowExtend;
	}
	/**
	 * Marks this element as abstract. Users never see abstract elements: they
	 * exist to simplify the description of other elements.
	 * 
	 * @param flag
	 *            true if the element is to be abstract, false if it is to be
	 *            concrete (user-visible)
	 */
	void setAbstract( boolean flag )
	{
		abstractElement = flag;
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.report.model.metadata.IObjectDefn#findProperty(java.lang.String)