I do not intend to use any scripts; my list of scripts is empty.
There should be an entry in the projects properties.
Right click your project in the management pane or activate it and click "Project -> Properties".
Switch to the "scripts" tab and make sure that there is no entry left.
The script is an autogenerated one.
You most likely have clicked (accidently) on "Add manual build script" in the "Libraries" tab of the properties dialog.
And later removed the "lib_finder.script".