Warning: No pixels are more than 50% selected. The selection edges will... - in actions and scripts

I do not know if they can be turned off in an Action.  A script may be able to turn warning dialogs off with code like this.  I wrote may because I'm not positive.  Un cough errors will be displayed

var orig_display_dialogs = app.displayDialogs;
app.displayDialogs = DialogModes.NO;		// Set Dialogs off
try { code(); } // run your code
// display error message if something goes wrong
catch(e) { alert(e + ': on line ' + e.line, 'Script Error', true); }
app.displayDialogs = orig_display_dialogs;	// Reset display dialogs 

This warning usually comes up when the value of the Feather is more than 0% or when the selection takes place on a layer with transparant pixels.