How to handle empty or null fields

I have a sql table with the following columns, job_no, job_department, job_date, job_name, job_location and job_description. I have designed a aras form where user key in the job_no, in the Job No. textbox field, a javascript method will run upon "on change" event to fetch the rest of the data. Issue I have now is that some of the fields are not being filled up and in sql table column, the fields are showing as null. When the javascript fetch in the data, Aras in internet explorer will prompt with error message "Internal Error:event handler failed", Technical message: event handler failed with message: unable to get property 'xml' of undefined or null reference" Stack Trace: "client side error" Aras in firefox will prompt with error message"Internal Error: event handler failed." Technical message: event handler failed with message: typeError: propval2 is undefined How to I handle this situation is some of the fields that the javascript is trying to fetch is empty or null? Below is my javascript: var inno = new Innovator(); var job_no=inno.newItem("st_JOB","get"); var textbox=this.value; if(!!textbox) { job_no.setProperty("job_no",textbox); job_no = job_no.apply(); } // var div_id = getFieldByName("job_no").id; // var control_id = div_id.substring(0, div_id.indexOf("span")); // var select = document.getElementById(control_id); // var job_no1 = select.value; // var job_no = inno.newItem("ST_JOB","get"); // job_no.setProperty("id",job_no1); // job_no = job_no.apply(); //**********Check if job number is valid**********// if(job_no.isError() || job_no.getItemCount() === 0) { alert("Job no. is not available!\nPlease try with valid job no!"); //getInputByName("job_department").value=""; //getInputByName("job_description").value=""; document.getElementsByName("job_department").value=""; handleItemChange("job_department",document.getElementsByName("job_department").value); document.getElementsByName("job_department").disabled="true"; document.getElementsByName("job_date").value=""; handleItemChange("job_date",document.getElementsByName("job_date").value); document.getElementsByName("job_date").disabled="true"; document.getElementsByName("job_name").value=""; handleItemChange("job_name",document.getElementsByName("job_name").value); document.getElementsByName("job_name").disabled="true"; document.getElementsByName("mm_vessel_name").value=""; handleItemChange("mm_vessel_name",document.getElementsByName("mm_vessel_name").value); document.getElementsByName("mm_vessel_name").disabled="true"; document.getElementsByName("job_description").value=""; handleItemChange("job_description",document.getElementsByName("job_description").value); document.getElementsByName("job_description").disabled="true"; job_no = null; document.getElementsByName("job_no").value=""; handleItemChange("job_no",document.getElementsByName("job_no").value); } //**********Check if job number is valid**********// else { //*********Check if job number is closed**********// document.getElementsByName("closed").value = job_no.getProperty("closed"); if(job_no.getProperty("closed")==='1') { //getInputByName("job_department").value=""; //getInputByName("job_date").value=""; //getInputByName("job_name").value=""; //getInputByName("mm_vessel_name").value=""; //getInputByName("job_description").value=""; //getInputByName("job_no").value=""; //getInputByName("closed").value=""; //document.getElementsByName("job_department").value=""; //document.getElementsByName("job_date").value=""; //document.getElementsByName("job_name").value=""; //document.getElementsByName("mm_vessel_name").value=""; //document.getElementsByName("job_description").value=""; //document.getElementsByName("job_no").value=""; //document.getElementsByName("closed").value=""; alert("Job no. had been closed!\nPlease select only 'Active' job no.!"); //job_no = job_no.remove(); //**********Check if job number is closed********// document.getElementsByName("job_department").value=""; handleItemChange("job_department",document.getElementsByName("job_department").value); document.getElementsByName("job_department").disabled="true"; document.getElementsByName("job_date").value=""; handleItemChange("job_date",document.getElementsByName("job_date").value); document.getElementsByName("job_date").disabled="true"; document.getElementsByName("job_name").value=""; handleItemChange("job_name",document.getElementsByName("job_name").value); document.getElementsByName("job_name").disabled="true"; document.getElementsByName("mm_vessel_name").value=""; handleItemChange("mm_vessel_name",document.getElementsByName("mm_vessel_name").value); document.getElementsByName("mm_vessel_name").disabled="true"; document.getElementsByName("job_description").value=""; handleItemChange("job_description",document.getElementsByName("job_description").value); document.getElementsByName("job_description").disabled="true"; document.getElementsByName("closed").value=""; handleItemChange("closed",document.getElementsByName("closed").value); document.getElementsByName("closed").disabled="true"; job_no = null; document.getElementsByName("job_no").value=""; handleItemChange("job_no",document.getElementsByName("job_no").value); return false; } handleItemChange("job_department",""); document.getElementsByName("job_department").value = job_no.getProperty("job_department"); handleItemChange("job_department",document.getElementsByName("job_department").value); document.getElementsByName("job_department").disabled="true"; handleItemChange("job_date",""); document.getElementsByName("job_date").value = job_no.getProperty("job_date"); handleItemChange("job_date",document.getElementsByName("job_date").value); document.getElementsByName("job_date").disabled="true"; handleItemChange("job_name",""); document.getElementsByName("job_name").value = job_no.getProperty("job_name"); handleItemChange("job_name",document.getElementsByName("job_name").value); document.getElementsByName("job_name").disabled="true"; handleItemChange("mm_vessel_name",""); document.getElementsByName("mm_vessel_name").value = job_no.getProperty("mm_vessel_name"); handleItemChange("mm_vessel_name", document.getElementsByName("mm_vessel_name").value); document.getElementsByName("mm_vessel_name").disabled="true"; handleItemChange("job_description",""); document.getElementsByName("job_description").value = job_no.getProperty("job_description"); handleItemChange("job_description",document.getElementsByName("job_description").value); document.getElementsByName("job_description").disabled="true"; } function getInputByName(inputName){ var allFields = document.getElementsByName(inputName); var requiredField; for (var i=0;i<allFields.length;i++){ if (allFields[i].tagName.toUpperCase()=="INPUT") { requiredField = allFields[i]; } } return requiredField; }