Created a field unique? There is no such thing as a unique field. Best you could do is validate it against other fields using code or query validation via CB Code Field or CB Query Field, which wouldn't have anything to do with latest CB release.
CB Code Field and CB Query Field were both improved to always run their validation even if the value is empty as it shouldn't have been skipping validation in that case. Your validation code should take this into account. For example if you don't want query validation being applied to empty values you can condition your query to check for that using an IF substitution. Example as follows.
[cb:if value!=""]QUERY VALIDATION HERE[/cb:if]
Will review just hardcoding this check in, but will need to implement a empty value check depending on the fieldtype since empty is very different depending on the field.
forge.joomlapolis.com/issues/7813