audio/avrcp: Fix crash if no player is available

It seems some Samsung Android devices may actually report no players
at all causing the following crash:

Program terminated with signal 11, Segmentation fault.
  #0  set_ct_player (player=0x0, session=<value optimized out>)
    at profiles/audio/avrcp.c:3139
  #1  0xb76c0aab in player_remove (data=0xb849a100)
    at profiles/audio/avrcp.c:3278
diff --git a/profiles/audio/avrcp.c b/profiles/audio/avrcp.c
index 6c8ed81..c100149 100644
--- a/profiles/audio/avrcp.c
+++ b/profiles/audio/avrcp.c
@@ -3200,7 +3200,8 @@
 
 	session->controller->player = player;
 	service = btd_device_get_service(session->dev, AVRCP_TARGET_UUID);
-	control_set_player(service, media_player_get_path(player->user_data));
+	control_set_player(service, player ?
+			media_player_get_path(player->user_data) : NULL);
 }
 
 static struct avrcp_player *create_ct_player(struct avrcp *session,
@@ -3330,6 +3331,10 @@
 	struct avrcp_player *player = data;
 	GSList *l;
 
+	/* Don't remove reserved player */
+	if (!player->id)
+		return;
+
 	for (l = player->sessions; l; l = l->next) {
 		struct avrcp *session = l->data;
 		struct avrcp_data *controller = session->controller;
@@ -3393,6 +3398,10 @@
 
 	g_slist_free_full(removed, player_remove);
 
+	/* There should always be an active player */
+	if (!session->controller->player)
+		create_ct_player(session, 0);
+
 	return FALSE;
 }