Yep.  Getting this error:
Any ideas/suggestions?
One Note:  Where you had “missing data” in AppleScript, I used “null” in JavaScript.
Is this correct?
I also tried an empty string “”, but got same results.
Actually JavaScript
'use strict';
var app = Application.currentApplication()
app.includeStandardAdditions = true
var myLib = Library('JMichael.Lib.JXA')
var MTLib = Library('Myriad Tables Lib')
myLib.helloJS("Called by JXA script")		// works fine
var theHeads = ["First Name", "Last Name", "Index", "Police", "Score", "Some Date"]
var theDate = new Date()
var someData = [
    ["Saga", "Norén", 1, true, 12.0, theDate],
    ["Rasmus", "Larsson", 2, true, 13.5, null],
    ["Freddie", "Holst", 3, false, 9.0, (theDate + 40000)],
    ["Claes", "Sandberg", 4, false, 1.23456789E+4, theDate + 50000],
    ["John", "Lundqvist", 5, true, 13.4567, theDate + 30000],
    ["Annika", "Melander", 6, false, 22.0, theDate + 60000]
	];
	
console.log(someData)
/*
--- AppleScript Code ---
set myTable to ¬
	make new table with data someData ¬
		with title "Sample table" column headings theHeads ¬
		with prompt ¬
		"You can drag/drop, select multiple rows. Everything is editable. Uses a row template" editable columns {} ¬
		row template {"", "", 1, true, 1.0, current date, missing value} ¬
		with multiple selections allowed, row numbering and empty selection allowed
*/
var myEditCol = []
var myRowTemplate = ["", "", 1, true, 1.0, theDate, null]
//*** NEXT LINE GIVES ERROR ***
//	Script Error
//	Error on line 45: Error: Script error.
var myTable = MTLib.makeNewTableWithData(someData,
		{withTitle: "Sample table",
		columnHeadings: theHeads,
		withPrompt: "You can drag/drop, select multiple rows. Everything is editable. Uses a row template",
		editableColumns: myEditCol,
		rowTemplate: myRowTemplate,
		multipleSelectionsAllowed: true, 
		rowNumbering: true,
		emptySelectionAllowed: true
		}
		);
REPLIES PANEL:
app = Application("Script Editor")
	app.displayAlert("From My JXA Lib:  Called by JXA script")
		--> {"buttonReturned":"OK"}
/* Saga,Norén,1,true,12,Sun Feb 14 2016 20:31:23 GMT-0600 (CST),Rasmus,Larsson,2,true,13.5,,Freddie,Holst,3,false,9,Sun Feb 14 2016 20:31:23 GMT-0600 (CST)40000,Claes,Sandberg,4,false,12345.6789,Sun Feb 14 2016 20:31:23 GMT-0600 (CST)50000,John,Lundqvist,5,true,13.4567,Sun Feb 14 2016 20:31:23 GMT-0600 (CST)30000,Annika,Melander,6,false,22,Sun Feb 14 2016 20:31:23 GMT-0600 (CST)60000 */
app = Application("Script Editor")
	app.alloc([])
		--> Error -1708: Message not understood.
Result:
Error -1753: Script error.