Setting a key to an empty array produces an error

[tuxmea]

# data/common.yaml
classes: []

Log file output:

[6fb91ddc-365a-4fad-96f2-198c2331b9f5] ActionView::Template::Error (undefined method `gsub!' for nil:NilClass):
[6fb91ddc-365a-4fad-96f2-198c2331b9f5]     20:         </div>
[6fb91ddc-365a-4fad-96f2-198c2331b9f5]     21:         <% hierarchy.files_for(node: @node).each do |file| %>
[6fb91ddc-365a-4fad-96f2-198c2331b9f5]     22:           <% index += 1 %>
[6fb91ddc-365a-4fad-96f2-198c2331b9f5]     23:           <% value = file.value_for(key: @key) %>
[6fb91ddc-365a-4fad-96f2-198c2331b9f5]     24:           <div class="card">
[6fb91ddc-365a-4fad-96f2-198c2331b9f5]     25:             <div class="card-header" id="path-<%= index %>">
[6fb91ddc-365a-4fad-96f2-198c2331b9f5]     26:               <h2 class="mb-0">
[6fb91ddc-365a-4fad-96f2-198c2331b9f5]
[6fb91ddc-365a-4fad-96f2-198c2331b9f5] app/models/hiera_data/yaml_file.rb:50:in `content_for_key'
[6fb91ddc-365a-4fad-96f2-198c2331b9f5] app/models/hiera_data/data_file.rb:5:in `content_for_key'
[6fb91ddc-365a-4fad-96f2-198c2331b9f5] app/models/hiera_data.rb:60:in `value_in_file'
[6fb91ddc-365a-4fad-96f2-198c2331b9f5] app/models/data_file.rb:50:in `value_for'
[6fb91ddc-365a-4fad-96f2-198c2331b9f5] app/views/keys/show.html.erb:23
[6fb91ddc-365a-4fad-96f2-198c2331b9f5] app/views/keys/show.html.erb:21:in `each'
[6fb91ddc-365a-4fad-96f2-198c2331b9f5] app/views/keys/show.html.erb:21
[6fb91ddc-365a-4fad-96f2-198c2331b9f5] app/views/keys/show.html.erb:13:in `each'
[6fb91ddc-365a-4fad-96f2-198c2331b9f5] app/views/keys/show.html.erb:13