TypeError in Devise::Registrations#edit

Question

I have a site where the user can add an avatar to himself through Gravatar. But, unfortunately, the form does not work for me ... I get an error like:

TypeError in Devise::Registrations#edit Showing /home/artem/projects/blog/app/views/devise/registrations/edit.html.erb where line #13 raised:

no implicit conversion of Enumerator into String

Application Trace | Framework Trace | Full Trace app/views/devise/registrations/edit.html.erb:13 app/views/devise/registrations/edit.html.erb:5

My form looks something like this:

<%= form_for(resource, as: resource_name, url: registration_path(resource_name), html: { method: :put }) do |f| %>
  <div class="form-group mt-4">
    <div class="row">
      <div class="col-sm-4">
    <% if resource.avatar.attached? %>
      <%= image_tag resource.avatar.variant(resize: "100x100!"), 
      class: "rounded-circle" %>
    <% else %>
      <%= image_tag gravatar_image_url(current_user.email.gsub(size: 100)),
      height: 100, 
      width: 100, 
      class: "rounded-circle" %>
        <% end %>
      </div>

      <div class="col-sm-5">
    <%= f.file_field :avatar %>
      </div>
    </div>
  </div>
  ...

<% end %>

Account system made by Devise.

Nothing is written about this, therefore, I don’t even know what I can try to solve the problem.

Fifth line: <%= form_for(resource, as: resource_name, url: registration_path(resource_name), html: { method: :put }) do |f| %>

13: <%= image_tag gravatar_image_url(current_user.email.gsub(size: 100)),