How to add a blank space in the drop-down in configurable list widget,?

In my form how to add a blank space while adding the options in the drop down in configurable list widget,I added a simple comma before the option list so it come through as a blank space in the form. but my form sometimes not showing the opted data in the drop down list of Configurable List widget ,Is that due to this?

Just add a comma without any characters to make it blank.

Here's an example:

The result:

You noticed that there's a blank space before the word "one". About the data missing when comma is added it should still show the data without any problems. Can you please share your form to us so we could check.