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 the flag is not set (undefined), and alerts appear for each call to STRPCCMD that fail when the configuration option, pui["pc command mode"], is undefined, "launcher", or "launcher_m2". Alerts appear as shown in this image:
Setting this flag to false causes error messages to appear in the browser console instead of in an alert, like shown below:
Where to set this configuration option? Here.