Inside error occured (client side): undefinedTypeError: object null is not iterable (cannot read property Symbol(Symbol.iterator))

Question

I am asking this from a QA point of view. I have a web application that I test with cypress.io.

When I access the localhost from outside Cypress, everything is ok. When I start the Cypress test, I get this error in the console of the browser:

Inside error occured (client side): undefinedTypeError: object null is not iterable (cannot read property Symbol(Symbol.iterator))

The code that I am executing is nothing fancy:

/// <reference types = "Cypress" />
    const constants = require("../support/constants");
    const data = require("../fixtures/muaOutput.json");
    const components = require("../support/components");

    describe('Login page', () => {
    beforeEach(() => {
        cy.visit(Cypress.env('muaUrl'));
        cy.login(data.muaEmail, data.muaPassword)
        if (cy.get(components.SAVE_BUTTON).length > 0) {
            cy.get(components.PIN_FIELD).clear().type('1234')
            cy.get(components.PIN_FIELD).clear().type('1234')
            cy.get(components.SAVE_BUTTON).click()
        } else {
            cy.contains(constants.MY_GARMENTS).should('be.visible')
        }
        sessionStorage.clear()
        cy.clearCookies()
        cy.clearLocalStorage()
    });

    it('1. Check if the title is present', () => {
        cy.contains(constants.PROFILE_TITLE).should('be.visible')
    });

    it('2. Verify elements on the home page', () => {
        cy.contains(constants.MY_GARMENTS).should('be.visible')
        cy.contains(constants.LOST_AND_FOUND).should('be.visible')

    });

    it('3. My Garments tests', () => {
        cy.get(components.MY_REPAIRS).click()
    })
})

Could this be an actual bug in the app? What is puzzling for me is that when I do these steps outside cypress, the errors do not appear in the console and everything works.