Need help with .Site.Data [solved]

I have this code in \layouts\_default\list.html:

        <h1>{{.Title}}</h1>
        {{ if ne ".Site.Data.persons.names .Title" nil }}
        <div class="term-listing-heading">{{ delimit (index .Site.Data.persons.names .Title) "<br />" }}
        </div>
        {{ end }}
        <ul class="li-article-list">
            {{ range .Data.Pages }}
                <li>
                    <time class="li-article-date">{{ .Date.Format "2/1 2006" }} г.</time>
                    <h4><a href="{{ .Permalink }}">{{ .Title }}</a></h4>
                </li>
            {{ end }}
        </ul>

This string in front matter:

---
persons: [ "Амфитеатров Александр Валентинович" ]
---

This strings in \data\persons\names.yaml:

"Амфитеатров Александр Валентинович":
  - "(1862–1938)"
  - "— беллетрист, драматург и фельетонист; после 1920 г. эмигрировал;"
  - "Cтр.: 117, 118, 120, 138, 148, 150, 152, 153, 158, 249, 261, 262, 265, 541."

It works well:

However, other tags that have no corresponding string in the names.yaml no longer work. Pages of other tags are no longer generated below the title.

Problem solved. Working code:

{{ if isset .Site.Data.persons.names .Title }}
  <div class="term-listing-heading">{{ delimit (index .Site.Data.persons.names .Title) "<br />" }}
  </div>
{{ end }}