SO: conditional option hiding in Sandbox extension

Am trying to restrict discard draft option available on Action menu of Order management page using below condition in expression builder in sandbox page composer of show button property:

#{bindings.SourceOrderSystem.inputValue.trim().toUpperCase() == 'ORA_ELECTRONIC_DOCUMENTS' ? false:true}

whenever am adding it and click on apply, the page is showing blank.

Is this common issue with expression builder condition. any help is highly appreciated.