Fix continuation for last page of playlists

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>