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
}
	/**
	 * Determines if this element can be dropped from its container.
	 * 
	 * @return <code>true</code> if it can be dropped. Returns
	 *         <code>false</code> otherwise.
	 */
	public boolean canDrop( )
	{
		
		
		if ( isRootIncludedByModule( ) )
			return false;
		
		
		if ( isVirtualElement( ) )
			return false;
		
		
		if ( container instanceof TemplateParameterDefinition )
		{
			assert containerSlotID == TemplateParameterDefinition.DEFAULT_SLOT;
			return false;
		}
		
		
		
		DesignElement element = this;
		if ( element instanceof TemplateParameterDefinition )
		{