Bug 146796 Error message pop up if display text contain non-digital char when add next item
Description: In decimal type parameter creation,display type is "list box", Error message pop up if "display text" contain non-digital char when add next item. Steps: 1.Create a new decimal parameter 2.Set display type as "list box" 3.Input one item: value:1, display text:test 4.Input another item: Value:2 Actual result: error message pop up: The display text already exists! Expected result: Input item succussfully.
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/ParameterDialog.java
createLabel( moreOptionSection, null ); 
		Composite checkBoxArea = new Composite( moreOptionSection, SWT.NONE );
		checkBoxArea.setLayout( UIUtil.createGridLayoutWithoutMargin( 2, false ) );
		checkBoxArea.setLayoutData( new GridData( GridData.FILL_BOTH ) );
		allowNull = new Button( checkBoxArea, SWT.CHECK );
		allowNull.setText( CHECKBOX_ALLOW_NULL );
		addCheckBoxListener( allowNull, CHECKBOX_ALLOW_NULL );
		allowBlank = new Button( checkBoxArea, SWT.CHECK );
		allowBlank.setText( CHECKBOX_ALLOW_BLANK );
		addCheckBoxListener( allowBlank, CHECKBOX_ALLOW_BLANK );
		doNotEcho = new Button( checkBoxArea, SWT.CHECK );
		doNotEcho.setText( CHECKBOX_DO_NOT_ECHO );
		addCheckBoxListener( doNotEcho, CHECKBOX_DO_NOT_ECHO );
		isHidden = new Button( checkBoxArea, SWT.CHECK );
		isHidden.setText( CHECKBOX_HIDDEN );
		addCheckBoxListener( isHidden, CHECKBOX_HIDDEN );
		needSort = new Button( checkBoxArea, SWT.CHECK );
		needSort.setText( CHECKBOX_SORT );
		addCheckBoxListener( needSort, CHECKBOX_SORT );
	}
	/**
	 * Set the input of the dialog, which cannot be null
	 * 
	 * @param input
	 *            the input of the dialog, which cannot be null
	 */
	public void setInput( Object input )
	{
		Assert.isNotNull( input );