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
target = newRef.getTargetStructure( );
			if ( target != null )
				target.addClient( this, prop.getName( ) );
		}
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.report.model.core.IPropertySet#setProperty(org.eclipse.birt.report.model.metadata.PropertyDefn,
	 *      java.lang.Object)
	 */
	public void setProperty( PropertyDefn prop, Object value )
	{
		setProperty( (ElementPropertyDefn) prop, value );
	}
	/**
	 * Clears the local value of the property. See <code>setProperty( )</code>
	 * for details. This is equivalent to calling
	 * <code>setProperty( propName, null )</code>.
	 * <p>
	 * Part of: Property value system.
	 * 
	 * @param propName
	 *            The name of the property to set. Must be valid. Can be a
	 *            system-defined or user-defined property name.
	 */
	public void clearProperty( String propName )
	{
		setProperty( propName, null );
	}