[8.1 14g][Bug] Tabs.lua:53 nil value

[darkancient]

It occurs when a chat tab is selected.

18x nibRealUI\Modules\Chat\Tabs.lua:53: attempt to index local 'tab' (a nil value)
nibRealUI\Modules\Chat\Tabs.lua:53: in function 'UpdateTab'
nibRealUI\Modules\Chat\Tabs.lua:111: in function <nibRealUI\Modules\Chat\Tabs.lua:105>
[C]:: in function 'FCF_OpenTemporaryWindow'
...Blizzard_PetBattleUI\Blizzard_PetBattleUI.lua:149: in function 'PetBattleFrame_Display'
...Blizzard_PetBattleUI\Blizzard_PetBattleUI.lua:95: in function <...Blizzard_PetBattleUI\Blizzard_PetBattleUI.lua:92>