Suitescript 2.0-Why is a new line inserted into a sublist on record edit - suitescript2.0

Question

I have the following client script deployed onto a vendor bill
/**
*#NApiVersion 2.x
*#NScriptType ClientScript
*/
define(["N/record"], function (record) {
/**
* #param {ClientScriptContext.fieldChanged} context
*/
function fieldChanged(context) {
//the if condition ensures the field changed trigger does not execute on changes in sublist. setting this to
//!context.sublistid ensures changes in department field and location field for the sublist do not trigger the script
if (
!context.sublistId &&
(context.fieldId == "department" || context.fieldId == "location")
) {
log.debug("sublistId", context.sublistId)
log.debug("fieldId", context.fieldId)
var recordObj = context.currentRecord
var departmentMain = recordObj.getValue({ fieldId: "department" })
var locationMain = recordObj.getValue({ fieldId: "location" })
var expenseSublist = recordObj.getSublist({ sublistId: "expense" })
var expenseSublistLength = recordObj.getLineCount({
sublistId: "expense",
})
log.debug("department", departmentMain)
log.debug("location", locationMain)
log.debug("expenseSublist.length", expenseSublistLength)
for (var i = 0; i < expenseSublistLength; i++) {
recordObj.selectLine({
sublistId: "expense",
line: i,
})
var departmentLine = recordObj.setCurrentSublistValue({
sublistId: "expense",
fieldId: "department",
value: departmentMain,
ignoreFieldChange: true,
})
var locationLine = recordObj.setCurrentSublistValue({
sublistId: "expense",
fieldId: "location",
value: locationMain,
ignoreFieldChange: true,
})
recordObj.commitLine({ sublistId: "expense" })
log.debug("department", departmentLine)
log.debug("location", locationLine)
}
}
}
/**
* #param {ClientScriptContext.postSourcing} context
*/
function postSourcing(context) {
var currentRecord = context.currentRecord
var sublistName = context.sublistId
var sublistFieldName = context.fieldId
var line = context.line
var departmentMain = currentRecord.getValue({ fieldId: "department" })
var locationMain = currentRecord.getValue({ fieldId: "location" })
if (sublistName === "expense" && sublistFieldName === "account") {
var expenseSublist = currentRecord.getSublist({ sublistId: "expense" })
var expenseSublistLength = currentRecord.getLineCount({
sublistId: "expense",
})
log.debug("department-main", departmentMain)
log.debug("location-main", locationMain)
currentRecord.setCurrentSublistValue({
sublistId: "expense",
fieldId: "department",
value: departmentMain,
ignoreFieldChange: false,
})
currentRecord.setCurrentSublistValue({
sublistId: "expense",
fieldId: "location",
value: locationMain,
ignoreFieldChange: false,
})
}
}
return {
fieldChanged: fieldChanged,
postSourcing: postSourcing,
}
})
When I edit an existing vendor bill record and attempt to save, I get the following prompt
It looks like placing the record into edit mode has also inserted a new blank line into the existing sublist despite no fields being clicked
Why would that be the case? Based on the above script, my expectation is that the postsourcing and field changed functions should only occur if the relevant fields (department and location for field changed and account for post sourcing) are clicked.
Is there something my script is missing?