TypeError: Cannot read properties of null (reading 'setTabColor')

I have minimal knowledge about coding or javascript but I tried to generate a code with ChatGPT but when I try to run it in google apps script it gives me an error saying: TypeError: Cannot read properties of null (reading 'setTabColor')

The script it supposed to create a google sheets for me.
This is the script I am trying to run:

function createTaskTracker() {
  // Create a new Google Sheets document
  var sheetName = "Task Tracker";
  var spreadsheet = SpreadsheetApp.create(sheetName);

  // Set up the tabs for the document
  var tabs = ["Overall", "Work", "Social Media", "Workout", "Freetime", "Long-Term         Progress"];
  for (var i = 0; i < tabs.length; i++) {
    var tabName = tabs[i];
    var sheet = spreadsheet.insertSheet(tabName);
  }

  // Set the tab colors to match the categories
  var colors = ["#ffffff", "#00ff00", "#0000ff", "#ffff00", "#ff0000"];
  var categoryTabs = ["Work", "Sports/Training", "Freetime", "Social Media"];
  for (var i = 0; i < categoryTabs.length; i++) {
    var categoryTab = categoryTabs[i];
    var colorIndex = i + 1;
    var sheet = spreadsheet.getSheetByName(categoryTab);
    var color = colors[colorIndex];
    sheet.setTabColor(color);
  }

  // Set up the column headers for each tab
  var headers = ["Task", "Routine", "Time Spent", "Status", "Progress"];
  var tabsWithHeaders = ["Work", "Sports/Training", "Freetime", "Social Media"];
  for (var i = 0; i < tabsWithHeaders.length; i++) {
    var tabName = tabsWithHeaders[i];
    var sheet = spreadsheet.getSheetByName(tabName);
    sheet.appendRow(headers);
  }

  // Freeze the first row on each tab
  for (var i = 0; i < tabs.length; i++) {
    var tabName = tabs[i];
    var sheet = spreadsheet.getSheetByName(tabName);
    sheet.setFrozenRows(1);
  }

  // Rename the default sheet to "Settings"
  var defaultSheet = spreadsheet.getSheetByName("Sheet1");
  defaultSheet.setName("Settings");

  // Add a message to the main tab
  var mainTab = spreadsheet.getSheetByName("Overall");
  mainTab.getRange("A1").setValue("Welcome to your Task Tracker!");
}

Since I have minimal knowledge about scripts I really had no solution or didn´t find a direct answer from a google search.

The issue is that when setting the tab colors, you have sheet name that doesn't exist in your current tabs/sheet names.

Initially, the tabs are set as:

var tabs = ["Overall", "Work", "Social Media", "Workout", "Freetime", "Long-Term Progress"];

The ones set to be colored are:

var categoryTabs = ["Work", "Sports/Training", "Freetime", "Social Media"];

Because Sports/Training doesn't exist, when it is called to have it's tab colored, it is not found (null).

Try this:

function createTaskTracker() {
const Spreadsheet = SpreadsheetApp.create(`Task Tracker`)
const headers = ["Task", "Routine", "Time Spent", "Status", "Progress"]
const tabs = [
{
Title: `Overall`,
TabColor: `#ffffff`,
HasHeaders: false
},
{
Title: `Work`,
TabColor: `#00ff00`,
HasHeaders: true
},
{
Title: `Social Media`,
TabColor: `#ff0000`,
HasHeaders: true
},
{
Title: `Workout`,
TabColor: `#0000ff`,
HasHeaders: true
},
{
Title: `Freetime`,
TabColor: `#ffff00`,
HasHeaders: true
},
{
Title: `Long-Term Progress`,
TabColor: `#ffffff`,
HasHeaders: true
},
]
tabs.forEach(tab => {
const newTab = Spreadsheet.insertSheet()
newTab.setName(tab.Title)
newTab.setTabColor(tab.TabColor)
if (tab.HasHeaders) {
newTab.appendRow(headers)
newTab.setFrozenRows(1)
}
})
Spreadsheet.deleteSheet(Spreadsheet.getSheetByName(`Sheet1`))
}