Adobe forms-checking that required fields are completed-Java Script

I have inserted two Java Scripts into my form--one for checking for required fields are completed, and then one for generating an email pulling a custom subject line, as shown below:

var emptyFields = [];

for (var i=0; i<this.numFields; i++) {

     var f= this.getField(this.getNthFieldName(i));

     if (f.type!="button" && f.required && f.display==display.visible) {

          if ((f.type=="text" && f.value=="") || (f.type=="checkbox" && f.value=="Off")) emptyFields.push(f.name);

     }

}

if (emptyFields.length>0) {

     app.alert("Error! You must fill in the following fields:\n" + emptyFields.join("\n"));

}

this.mailDoc({bUI:false,cTo:"xx@bcbsks.com,Jackie.Williams@xx.com,xx@xx.com",cSubject:"Bugzilla Form for: "+this.getField("Bugzilla Title").value+" - "+this.getField("Bugzilla ID").value})

Issue: After the error window displays fields that have not been completed, when I click OK the email window displays.

QUESTION: How can I stop the email window from displaying until all fields are completed?

THANKS!