JMeter: While condition with property value

I currently have a problem with While Controller in JMeter I have a While Controller with many steps inside it, the final step has a BeanShell Assertion with something like this

${__setProperty(sessionUID_global,${sessionUID})};

I'm trying to put a condition for While Controller like this:

${__javaScript(vars.get("sessionUID_global") == null)}

But, It's not working Could anyone help me to stop the while controller with a condition when sessionUID_global has a value?

Thank you