Freagarach noticed in an svn game earlier 'today', an error message can be triggered while the aiconfig page is opened.
```
ERROR: JavaScript error: gui/gamesetup/gamesetup.js line 2479
TypeError: ai is undefined
openAIConfig/<@gui/gamesetup/gamesetup.js:2479:8
updateGUIObjects@gui/gamesetup/gamesetup.js:2440:3
handlePlayerAssignmentMessage@gui/gamesetup/gamesetup.js:1698:2
g_NetMessageTypes.players@gui/gamesetup/gamesetup.js:145:20
handleNetMessages@gui/gamesetup/gamesetup.js:2115:4
onTick@gui/gamesetup/gamesetup.js:2087:3
__eventhandler18 (tick)@setupWindow tick:0:1
`` `
The error can be reproduced by opening the aiconfig dialog with a client, then having the host unassign the AI from that slot.
The error is caused by the behavior change in rP22676/D1684 that unified the two PopGUIPage calls - the one that does call the callback and the one that doesn't.
Now the callback is called in both cases, so `ai` will be undefined when that `PopGuiPage()` call is triggered and `g_LastViewedAIPlayer` will always be -1 when the page had been closed.