Look up SharePoint list has several columns. Each column is to be used as a look up data source for a drop down or multiple-selection list box (the exact control type is irrelevant) in an Infopath 2013 form.
Some columns do not have the same number of populated fields. For instance, one column has 50 items, and another column has 10 items.
For the Infopath control that looks up in the list column that has 10 items, even with ticking in the control properties
Show only entries with unique display names
the drop down list box displays the 10 items as predicted + one empty item, as the 40 (50-10) empty items are understood by the look up as a 'display name'. This empty item can be selected as a valid answer when the form is being filled in.
What's the best way to prevent this empty field to display?
Is it only a matter of creating different look up lists (and having various data in the same look up as the data source is bad practice), and there should be a separate SharePoint custom list for each data source needed for various Infopath controls?