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
String type = null;
		if ( StringUtil.isBlank( dataTypeChooser.getText( ) ) )
		{
			type = inputParameter.getDataType( );
		}
		else
		{
			IChoice choice = dataType.findChoiceByDisplayName( dataTypeChooser.getText( ) );
			type = dataType.findChoiceByDisplayName( dataTypeChooser.getText( ) )
					.getName( );
			type = choice.getName( );
		}
		return type;
	}
	/**
	 * Gets the internal name of the control type from the display name
	 */
	private String getSelectedControlType( )
	{
		String displayText = controlTypeChooser.getText( );
		if ( StringUtil.isBlank( displayText ) )
		{
			return getInputControlType( );
		}
		if ( DISPLAY_NAME_CONTROL_COMBO.equals( displayText ) )
		{
			return PARAM_CONTROL_COMBO;
		}
		if ( DISPLAY_NAME_CONTROL_LIST.equals( displayText ) )
		{