Bug 138562 Splite extendsexcpetion to seperate sub class
The suggestion is Parent invalid Cycle extends Different type extends Not top level extends
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/DesignElement.java
* the method will simply return a null property value.
	 * <p>
	 * The search won't search up the inheritance hierarchy if the property is
	 * defined to not inherit.
	 * <p>
	 * Part of: Property value system.
	 * 
	 * @param module
	 *            the module
	 * @param propName
	 *            name of the property to get. Can be a system-defined or
	 *            user-defined property name. Must be of the correct case.
	 * @return The property value, or null if no value is set.
	 */
	public Object getProperty( Module module, String propName )
	{
		ElementPropertyDefn prop = getPropertyDefn( propName );
		
		if ( prop == null )
			return null;
		return getProperty( module, prop );
	}
	/**
	 * Gets a property value given its definition. This version does the full
	 * property search as defined by the given derived component. That is, it
	 * gets the "effective" property value. The definition can be for a system
	 * or user-defined property.
	 * <p>
	 * The search won't search up the inheritance hierarchy if the non-style
	 * property is defined to not inherit. And style property won't be searched