Change Swatch Names Script

I think "try" and "catch" might be what you need. Here's an example, not changing names, but you get the idea.

var swatch;
try {
    swatch = app.activeDocument.swatches.getByName("mySwatch");
} catch (error) {
    // do something? or keep quiet?
}
if ( swatch != undefined) {
    // do somethng with the swatch!
}

Edit: I seem to recall there might be times where Try/Catch doesn't stop Illustrator complaining. In those cases, take the time to check variables before using, eg. are they undefined, or null, to avoid the error altogether. This is probably a good practice anyway. So if you are changing names, check to see if the name is unique (or whatever your error is) before doing it.

 Regards,

Mark