The flag, pui["alert pccommand errors"], can be set to false to prevent alerts from appearing when a program on the server attempts to call STRPCCMD and no Listener or Launcher is setup on the user's PC.
By default, alerts appear for each call to STRPCCMD that fail when pui["pc command mode"] is undefined, "launcher", or "launcher_m2".
Setting this flag to false causes error messages to appear in the browser console instead of in an alert.
Example
pui["alert pccommand errors"] = false;
Where to set this configuration option? Here.