removeInputError (input) {
    /* Get the parent element. Should most likely be a <div class="input-field" ... />. */
    const parent = input.parentElement

    if (!parent) return

    /* Remove all elements having class .error-text. */
    const els = parent.getElementsByClassName('error-text')
    for (let i = 0; i < els.length; i++) { parent.removeChild(els[i]) }
  }
Removes any error message from the specified input element.

@param {HTMLElement} input The input element that previously caused the error.