Image buttons are redering with input classes

The issue is that image_button is rendering to the DOM with the input classes defined in the theme's input__bulma function. Causing the image buttons to render out with the icons (see attached screenshot).

It appears this issue can be resolved by adding the image_button to the $exclude_input array in the bulma_theme_suggestions_input_alter theme function.

The rendered markup with classes on a webform:

  <div class="control has-icons-left">
    <input data-drupal-selector="edit-superficial-mass-changes-items-0-operations-add" formnovalidate="formnovalidate" type="image" id="edit-superficial-mass-changes-items-0-operations-add--T9MzCbIv3LU" name="superficial_mass_changes_table_add_0" src="/modules/contrib/webform/images/icons/plus.svg" alt="Add" title="Add" class="image-button js-form-submit form-submit input">
            <span class="icon is-left">
            <i class="fa fa-keyboard-o"></i>
        </span>
    </div>