MainUI check for Null value to set visibility

I try to set a oh-list-item to be visible depending whether a certain item contains a value or is NULL. It was easy to check for specific values but I fail to check for NULL. Could someone please advise how a expression to check for an item NULL value would look like?


Pretty much the same as checking for specific values only using "NULL". Show what you’ve tried.

Also, keep in mind that all values returned by the items object in the widget expressions are strings. So, you are not actually comparing to a value of NULL but a string "NULL".

This was the relevant hint. Thanks