clean up ACK error coding a little bit

git-svn-id: https://svn.musicpd.org/mpd/trunk@1321 09075e82-0dd4-0310-85a5-a0d7c8717e4f

src/player.c

@@ -386,8 +386,7 @@ int playerSeek(FILE * fp, Song * song, float time) {
 	PlayerControl * pc = &(getPlayerData()->playerControl);
 
 	if(pc->state==PLAYER_STATE_STOP) {
-		myfprintf(fp,"%s player not currently playing\n",
-				COMMAND_RESPOND_ERROR);
+		commandError(fp, "player not currently playing");
 		return -1;
 	}