NoMethodError in Frontend#category

Showing /var/www/clients/client1/web1/web/www/app/apps/plugins/contact_form/views/forms_shorcode.html.erb where line #81 raised:

undefined method `[]' for nil:NilClass
Extracted source (around line #81):
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var previous_submit_text = _this.text();
_this.text("<%= _t[:sending] %>")
_this.attr('disabled', 'disabled');
$(".flash_messages").remove();

Trace of template inclusion: app/apps/themes/launch_de/views/template_standard.html.erb

Rails.root: /var/www/clients/client1/web1/web/www

Application Trace | Framework Trace | Full Trace

Request

Parameters:

{"format"=>"html",
 "slug"=>"fair-rueckte-mitgliedschaft"}

Response

Headers:

None