Crash on summoning non-existent buttons

[mightyjoe781]

ERROR[Main]: ServerError: AsyncErr: ServerThread::run Lua: "basic_robot:button_256" is not a registered node!

[mightyjoe781]

Hello This issue still existing on your latest commit.
Put this in basic_robot and execute.

pos = self.pos()
pos.x = pos.x + 1
pos.y = pos.y + 1
pos.z = pos.z + 1
keyboard.set(pos,3000)
self.remove()

One possible way maybe is to check if the node keyboard is about to set even exists in registered node table.