Bug 142432 MasterPage from library can't be restored to modify
Details: MasterPage from library can't be restored to modify Step: 1.New a library named lib1, and insert a masterpage named lib-mp. 2.Publish the library into resource folder. 3.New a report design and use lib1. 4.Drop the lib-mp from library explorer into outline of report design. 5.Double click lib-mp, and switch to Property editro tab. 6.Click restore. Actual result: Pop up an error message and said that the master page cannot specify size the page type is not custom.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/DesignElementHandle.java
* 
	 * @return <code>true</code> if this element is valid, otherwise
	 *         <code>false</code>.
	 */
	public boolean isValid( )
	{
		return getElement( ).isValid( );
	}
	/**
	 * Determines whether to show an error item on the element or not. Show an
	 * error item if the element is invalid or has semantic errors, otherwise
	 * not.
	 * 
	 * @return true if the element has semantic error or the element is invalid
	 */
	public boolean showError( )
	{
		return hasSemanticError( ) || !isValid( );
	}
	/**
	 * Sets the status that identifies whether the element is valid or not.
	 * 
	 * @param isValid
	 *            the status to set
	 */
	public void setValid( boolean isValid )
	{
		getElement( ).setValid( isValid );
	}
	/**