LUA HTTP Interface: If <id> is omitted at the status.xml play command, play...

LUA HTTP Interface: If <id> is omitted at the status.xml play command, play last active item instead of first playlist item.
Signed-off-by: Rémi Duraffort <ivoire@videolan.org>

share/lua/http/requests/README.txt

@@ -23,7 +23,7 @@ status.xml:
 > add <mrl> to playlist:
   ?command=in_enqueue&input=<mrl>
 
-> play playlist item <id>:
+> play playlist item <id>. If <id> is omitted, play last active item:
   ?command=pl_play&id=<id>
 
 > toggle pause. If current state was 'stop', play item <id>:

share/lua/http/requests/status.xml

@@ -55,7 +55,11 @@ if command == "in_play" then
 elseif command == "in_enqueue" then
   vlc.playlist.enqueue({{path=stripslashes(input),options=options}})
 elseif command == "pl_play" then
+  if id == -1 then
+    vlc.playlist.play()
+  else
     vlc.playlist.goto(id)
+  end
 elseif command == "pl_pause" then
   vlc.playlist.pause()
 elseif command == "pl_stop" then