Bug 151959 inappropriate screen operation
steps to reproduce: - create a report - add a grid item (3x3) - switch to Outline view - expand the grid item to see its rows and cells - select the grid item, and drag it into any of its own cell expected behavior: - is it an invalid screen operation? if it is, it should be banned actual behavior: - the grid item was disappeared surprisingly
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/DesignElement.java
* @return Returns the idRef.
	 */
	public long getBaseId( )
	{
		return baseId;
	}
	/**
	 * Clears local properties of the element.
	 */
	public void clearAllProperties( )
	{
		this.name = null;
		this.extendsRef = null;
		propValues.clear( );
	}
	/**
	 * Determines whether this element and its contents are managed by
	 * namespace. If this element is a pending node and not in any module, or it
	 * is contained in a slot that is not managed by namespace, then return
	 * false. Otherwise true.
	 * 
	 * @param slotID
	 *            the slot ID in this element
	 * @return true if this element and its contents are managed by namespace,
	 *         otherwise false
	 */
	public boolean isManagedByNameSpace( int slotID )
	{
		
		if ( getRoot( ) == null )