function UIFax:choice(choice,additionalInfo)

  .......

  -- VIP may choose to visit anyway if he is refused too often
  elseif (self.ui.hospital.vip_declined > 2 and vip_ignores_refusal == 2) and choice == "refuse_vip" then
    self.ui.hospital.num_vips = self.ui.hospital.num_vips + 1
    self.ui.app.world:spawnVIP(additionalInfo.name)    <------------ CRASH
    self.ui.hospital.vip_declined = 0
  elseif choice == "refuse_vip" then
    self.ui.app.world:nextVip() -- don't start an inspection
    self.ui.hospital.vip_declined = self.ui.hospital.vip_declined + 1
  elseif choice == "accept_vip" then
    self.ui.hospital.num_vips = self.ui.hospital.num_vips + 1
    self.ui.app.world:spawnVIP(additionalInfo.name)          <------------- but this is the same call for accepting


-- Removes the Message, executing a choice if given, else just deletes it
--!param choice_number (number) if given, removes the message by executing this choice.
function UIMessage:removeMessage(choice_number)
  if choice_number then
    if not self.fax then
      self.fax = UIFax(self.ui, self) -- NB: just create, don't add to ui
    end
    self.fax:choice(self.message.choices[choice_number].choice)     <---- Caller of the CRASH
  else



Function creating the invitation
Both choices have the "additionalInfo" field.

-- Creates VIP and sends a FAX to query the user.
function Hospital:createVip()
  local vipName =  _S.vip_names[math.random(1,10)]
  local message = {
    {text = _S.fax.vip_visit_query.vip_name:format(vipName)},
    choices = {{text = _S.fax.vip_visit_query.choices.invite, choice = "accept_vip", additionalInfo = {name=vipName}},
               {text = _S.fax.vip_visit_query.choices.refuse, choice = "refuse_vip", additionalInfo = {name=vipName}}}
  }
  -- auto-refuse after 20 days
  self.world.ui.bottom_panel:queueMessage("personality", message, nil, 24*20, 2)
end