Fix Rate property on org.mpris.MediaPlayer2.Player

Rate should never be 0.0 (according to the spec), so we pick a sensible
default when we do not have a current track: 1.0.

Also, when the current item changes, the Rate may also change.  So add
it to the PropertiesChanged signal just to be sure.
Signed-off-by: Mirsal Ennaime <mirsal@videolan.org>
(cherry picked from commit 8f754d8715c72abc4ba1b0f26ae136c1db41437b)
Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>

modules/control/dbus/dbus.c

@@ -506,6 +506,11 @@ static void ProcessEvents( intf_thread_t *p_intf,
         {
         case SIGNAL_ITEM_CURRENT:
             TrackChange( p_intf );
+
+            // rate depends on current item
+            if( !vlc_dictionary_has_key( &tracklist_properties, "Rate" ) )
+                vlc_dictionary_insert( &player_properties, "Rate", NULL );
+
             vlc_dictionary_insert( &player_properties, "Metadata", NULL );
             break;
         case SIGNAL_INTF_CHANGE:

modules/control/dbus/dbus_player.c

@@ -523,7 +523,7 @@ MarshalRate( intf_thread_t *p_intf, DBusMessageIter *container )
         vlc_object_release( (vlc_object_t*) p_input );
     }
     else
-        d_rate = 0.;
+        d_rate = 1.0;
 
     dbus_message_iter_append_basic( container, DBUS_TYPE_DOUBLE, &d_rate );
 }