Revert "ui.tools.listener: removing unnecessary spawn."
Revert "ui.tools.listener: removing unnecessary spawn."

This reverts commit f8aa8038d3de8fdb796c59f9fbda04e25edda1b3.
Breaks error handling: http://paste.factorcode.org/paste?id=2407

mcandre/factor,mcandre/factor,mcandre/factor,mcandre/factor,mcandre/factor,mcandre/factor,mcandre/factor