Bug 180864 Change Allow Null option in Cascading Group.[0705]
Description: Change Allow Null option in Cascading Group. Build number:2.2.0.v20070404 Steps to reproduce: 1. New a cascading group and add sub parameter. Expected result: Is Required option in cascading group definition dialog. Actual result: Allow null value option in Cascading Group definition dialog Error log:N/A
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/CascadingParametersDialog.java
int len = UIUtil.getMaxStringWidth( string, control );
		return len;
	}
	/**
	 * 
	 * Constructor.
	 * 
	 * @param parentShell
	 * @param title
	 */
	public CascadingParametersDialog( Shell parentShell, String title )
	{
		super( parentShell, title );
	}
	/**
	 * Constructor.
	 * 
	 * @param title
	 */
	public CascadingParametersDialog( String title )
	{
		super( title );
	}
	protected Control createDialogArea( Composite parent )
	{
		Composite composite = (Composite) super.createDialogArea( parent );
		UIUtil.bindHelp( parent, IHelpContextIds.CASCADING_PARAMETER_DIALOG_ID );
		GridData data = new GridData( );
		data.widthHint = 600;
		maxStrLengthProperty = getMaxStrLength( PROPERTY_LABEL_STRING,