Ajax Errors break Apply button on View modal & autocomplete itself

Merely activating this module seems to break basic Views functionality for me.
If installed, clicking the Apply button or Cancel on the configuration modal for the filter briefly shows a spinner, but the modal doesn't go away. In my console, I see this:

AjaxError: 
An AJAX HTTP error occurred.
HTTP Result Code: 200
Debugging information follows.
Path: /gbr/en/admin/structure/views/ajax/handler/resource_center_articles/page_1/filter/title
StatusText: OK
ResponseText: 
Warning:  call_user_func_array() expects parameter 1 to be a valid callback, function 'element_validate_integer' not found or invalid function name in /var/www/delphi/web/core/lib/Drupal/Core/Form/FormValidator.php on line 282
[{"command":"closeDialog","selector":"#drupal-modal","persist":false},{"command":"viewsShowButtons","changed":true},{"command":"viewsTriggerPreview"},{"command":"insert","method":"html","selector":"#views-tab-page_1","data":"\u003Cdiv id=\u0022edit-display-settings-details\u0022\u003E\u003Cdiv id=\u0022edit-display-settings-top\u0022 class=\u0022views-ui-display-tab-actions edit-display-settings-top views-ui-display-tab-bucket clearfix\u0022\u003E  \u003Cdiv class=\u0022dropbutton-wrapper\u0022\u003E\u003Cdiv class=\u0022dropbutton-widget\u0022\u003… ajax.js:98:32 

I can forcibly close the modal with the X at the upper right, and any changes that were made seem to have been applied.

I searched my site's codebase, and can confirm that the only place 'element_validate_integer' shows up is line 79 of views_autocomplete_filters/src/Plugin/views/filter/ViewsAutocompleteFiltersTrait.php where I presume it's being claimed to exist as a function, but no actual function exists.