Description:
When I upgraded our ExpressionEngine & Publisher module, the search function stopped working. I assume this has something to do with the Publisher Module since the error outputted the following message:

<b>Fatal error</b>:  Uncaught Error: Class 'EEBlocks\Helper\App' not found in httpdocs/system/user/addons/publisher/legacy/libraries/Publisher_search.php:162
Stack trace:
#0 httpdocs/system/user/addons/publisher/ext.publisher.php(778): Publisher_search->modify_search_query('SELECT\n\t\t\tDISTI…', 'd5f349525c4996b…')
#1 httpdocs/system/ee/legacy/libraries/Extensions.php(221): Publisher_ext->channel_search_modify_search_query('SELECT\n\t\t\tDISTI…', 'd5f349525c4996b…')
#2 httpdocs/system/ee/legacy/libraries/Extensions.php(116): EE_Extensions->call_class('Publisher_ext', 'channel_search_…', Array, Array)
#3 httpdocs/system/ee/EllisLab/Addons/search/mod.search.php(1010): EE_Extensions->call('channel_search_…', 'SELECT\n\t\t\tDISTI…', 'd5f349525c4996b…')
#4 httpdocs/system/ee/EllisLab/Addons/search/mod.search.php(1124): Sear in <b>httpdocs/system/user/addons/publisher/legacy/libraries/Publisher_search.php</b> on line <b>162</b><br />

And line 162 in file Publisher_search contains ‘if (\EEBlocks\Helper\App::isEE3()) {'

The search form was built with the following code:

{exp:search:simple_form form_class="navbar-form navbar-right" channel="home|pages|industries|cases|materials|blog|news|about|faq" no_result_page="search/no_results" result_page="search/index" search_in="everywhere"}
                <div class="form-group hidden">
                  <input type="text" class="form-control" name="keywords" placeholder="{phrase:search}">
                </div>
                <button type="submit" class="btn as-search"><i class="fa fa-search"></i></button>
{/exp:search:simple_form}