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
.validateForAdding( getHandle( module ), propDefn, list, toAdd );
		if ( errorList.size( ) > 0 )
		{
			throw (PropertyValueException) errorList.get( 0 );
		}
	}
	/**
	 * Checks the parent element.
	 * 
	 * @param parent
	 *            the parent element
	 * @return <true> if the parent element is <code>NOT_FOUND</code>,<code>WRONG_TYPE</code>,
	 *         <code>SELF_EXTEND</code>,<code>CIRCULAR</code>. Otherwise
	 *         <code>false</code>.
	 */
	private boolean isExtendsValid( DesignElement parent )
	{
		try
		{
			checkExtends( parent );
		}
		catch ( ExtendsException e )
		{
			return false;
		}
		return true;
	}
	/**
	 * Checks the parent element.
	 *