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
choiceSet = DesignEngine.getMetaDataDictionary( )
					.getChoiceSet( DesignChoiceConstants.CHOICE_NUMBER_FORMAT_TYPE );
		}
		return choiceSet;
	}
	private void updateFormatField( )
	{
		String displayFormat;
		String previewString;
		String type = getSelectedDataType( );
		IChoiceSet choiceSet = getFormatChoiceSet( getSelectedDataType( ) );
		if ( choiceSet == null )
		{
			displayFormat = DesignEngine.getMetaDataDictionary( )
					.getChoiceSet( DesignChoiceConstants.CHOICE_STRING_FORMAT_TYPE )
					.findChoice( DesignChoiceConstants.STRING_FORMAT_TYPE_UNFORMATTED )
					.getDisplayName( );
			previewString = "True"; 
		}
		else
		{
			displayFormat = choiceSet.findChoice( formatCategroy )
					.getDisplayName( );
			if ( defaultValue != null )
			{
				previewString = format( defaultValue );
			}
			else
			{
				if ( formatCategroy == DesignChoiceConstants.STRING_FORMAT_TYPE_CUSTOM