corsicorsari Hi. This is not a coding error. It is from configuration and have no impact on the functionality. Basically in a place where script is prepared to work with multiple selection while system is only providing one option. It's this kind of the issue. But again it's nothing alarming. The message is showing because only as a warning, so easiest is to simply hide it.
If this warning will be coming with a line number for the code than I may be able to help more and hide it in code simply by adding "@" in front of this line.