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
ContentCommand cmd = new ContentCommand( module, container );
		cmd.remove( element, slotID, false );
	}
	/**
	 * Drops this element from the design. Removes the element from its
	 * container and name space, if any.
	 * <p>
	 * Note: If this element is referenceable, the property referring it will be
	 * unresolved.
	 * 
	 * @throws SemanticException
	 *             if this element has no container or the element cannot be
	 *             dropped.
	 * @see SlotHandle
	 * @see #dropAndClear()
	 */
	public void drop( ) throws SemanticException
	{
		DesignElement element = getElement( );
		DesignElement container = element.getContainer( );
		if ( container == null )
			throw new ContentException( element, -1,
					ContentException.DESIGN_EXCEPTION_HAS_NO_CONTAINER );
		int slotID = element.getContainerSlot( );
		assert slotID != -1;
		ContentCommand cmd = new ContentCommand( module, container );
		cmd.remove( element, slotID, true );
	}
	/**
	 * Finds the slot within this element that contains the given element.