Fix continuation for last page of playlists

src/invidious/channels.cr

@@ -375,14 +375,15 @@ def fetch_channel_playlists(ucid, author, auto_generated, continuation, sort_by)
     json = JSON.parse(response.body)
 
     if json["load_more_widget_html"].as_s.empty?
-      return [] of SearchItem, nil
-    end
-
+      continuation = nil
+    else
       continuation = XML.parse_html(json["load_more_widget_html"].as_s)
       continuation = continuation.xpath_node(%q(//button[@data-uix-load-more-href]))
+
       if continuation
         continuation = extract_channel_playlists_cursor(continuation["data-uix-load-more-href"], auto_generated)
       end
+    end
 
     html = XML.parse_html(json["content_html"].as_s)
     nodeset = html.xpath_nodes(%q(//li[contains(@class, "feed-item-container")]))

src/invidious/views/playlists.ecr

@@ -85,7 +85,7 @@
 <div class="pure-g h-box">
     <div class="pure-u-1 pure-u-md-4-5"></div>
     <div class="pure-u-1 pure-u-lg-1-5" style="text-align:right">
-        <% if items.size >= 28 %>
+        <% if continuation %>
             <a href="/channel/<%= channel.ucid %>/playlists?continuation=<%= continuation %><% if sort_by != "last" %>&sort_by=<%= sort_by %><% end %>">
                 <%= translate(locale, "Next page") %>
             </a>