Lubuntu eclipse problem on package explorer Show in System Explorer

If you use Lubuntu 18.04 and eclipse and want to navigate from package explorer to the System Explorer and get an error dialog that the command cant be executed you can do the following to solve this problem.

Go to menu Window->Preferences. Under General -> Workspace enter in the text field with label 'Command for launching system explorer:' the following:

pcmanfm ${selected_resource_uri}

Apply and close. This should solve the problem