Avoid rendering extraneous separators

handling cases where the artist or album data might be missing to avoid
rendering extraneous separators. Suggested by Copilot.

Author: matlads

beetsplug/web/templates/index.html

@@ -39,7 +39,11 @@ <h1>beets</h1>
         <div id="extra-detail"></div>
         <!-- Templates. -->
         <script type="text/template" id="item-entry-template">
-            <%= artist %> &ndash; <%= album %> &ndash; <%= title %>
+            <% if (artist) { %><%= artist %><% } %>
+            <% if (artist && album) { %> &ndash; <% } %>
+            <% if (album) { %><%= album %><% } %>
+            <% if ((artist || album) && title) { %> &ndash; <% } %>
+            <%= title %>
             <span class="playing">&#9654;</span>
         </script>
         <script type="text/template" id="item-main-detail-template">