Have you even added a value? Meaning have you added a name to the teleport? It's saying null because there is no value to go with it.
It's handled in player assistant.
Here is an example of mine
c.getPA().sendFrame126("Monster Teleport", 13037);
c.getPA().sendFrame126("Minigame Teleport", 13047);
c.getPA().sendFrame126("Boss Teleport", 13055);
c.getPA().sendFrame126("Pking Teleport", 13063);
c.getPA().sendFrame126("Skill Teleport", 13071);
c.getPA().sendFrame126("Monster Teleport", 1300);
c.getPA().sendFrame126("Minigame Teleport", 1325);
c.getPA().sendFrame126("Boss Teleport", 1350);
c.getPA().sendFrame126("Pking Teleport", 1382);
c.getPA().sendFrame126("Skill Teleport", 1415);
}