Fix missing .id to retrieve first playlist video ID

This was missed in the review of PR 5196

src/invidious/frontend/watch_page.cr

@@ -32,7 +32,7 @@ module Invidious::Frontend::WatchPage
     return String.build(4000) do |str|
       str << "<form"
       str << " class=\"pure-form pure-form-stacked\""
-      str << " action='" << URI.encode_www_form(url) << "'"
+      str << " action='#{url}'"
       str << " method='post'"
       str << " rel='noopener'"
       str << " target='_blank'>"

src/invidious/routes/embed.cr

@@ -20,7 +20,7 @@ module Invidious::Routes::Embed
         return error_template(500, ex)
       end
 
-      url = "/embed/#{first_playlist_video}?#{env.params.query}"
+      url = "/embed/#{first_playlist_video.id}?#{env.params.query}"
 
       if env.params.query.size > 0
         url += "?#{env.params.query}"