2x Guildbook\Guildbook_Core.lua:341: attempt to index field '?' (a nil value)
Guildbook\Guildbook_Core.lua:341: in function <Guildbook\Guildbook_Core.lua:314>
[C]: ?
[C]: ?
[C]: ?
[C]: ?
[C]: ?
...\ArkInventory\Externals\Ace3\AceHook\AceHook-3.0-9.lua:95: in function <...\ArkInventory\Externals\Ace3\AceHook\AceHook-3.0.lua:87>
[C]: ?

Locals:
self = GameTooltip {
0 =
SetText = defined =[C]:-1
SetHyperlink = defined =[C]:-1
SetTradeSkillItem = defined =[C]:-1
hasMoney = 1
comparing = false
Hide = defined =[C]:-1
SetCraftItem = defined =[C]:-1
SetQuestRewardSpell = defined @BootyBayGazette\libs\LibExtraTip\LibExtraTip.lua:419
SetQuestLogRewardSpell = defined @BootyBayGazette\libs\LibExtraTip\LibExtraTip.lua:419
SetShapeshift = defined @BootyBayGazette\libs\LibExtraTip\LibExtraTip.lua:419
ClearLines = defined =[C]:-1
LibExtraTipLeft =

{
}
ARKTTD = {
}
Show = defined =[C]:-1
__hasEPGPTooltip = false
SetPetAction = defined @BootyBayGazette\libs\LibExtraTip\LibExtraTip.lua:419
SetUnitDebuff = defined =[C]:-1
SetItemByID = defined =[C]:-1
SetLootItem = defined =[C]:-1
SetQuestItem = defined =[C]:-1
default = 1
SetTrainerService = defined =[C]:-1
numMoneyFrames = 1
TopOverlay = {
}
LibExtraTipRight = {
}
SetInboxItem = defined =[C]:-1
SetBuybackItem = defined =[C]:-1
shoppingTooltips = {
}
ttGradient = {
}
SetMerchantItem = defined =[C]:-1
SetMerchantCostItem = defined =[C]:-1
FadeOut = defined =[C]:-1
BottomOverlay = {
}
SetTalent = defined @BootyBayGazette\libs\LibExtraTip\LibExtraTip.lua:419
SetTradePlayerItem = defined =[C]:-1
SetIconTextureAndText = defined @TipTacItemRef\ttItemRef.lua:62
SetSendMailItem = defined =[C]:-1
SetQuestLogItem = defined =[C]:-1
updateTooltip = 0.016000
SetInventoryItem = defined =[C]:-1
SetTradeTargetItem = defined =[C]:-1
ttCount = {
}
SetLootRollItem = defined =[C]:-1
SetUnitAura = defined =[C]:-1
SetCraftSpell = defined =[C]:-1
SetAuctionSellItem = defined =[C]:-1
SetBagItem = defined =[C]:-1
needsReset = true
SetAction = defined =[C]:-1
ttIcon = {
}
SetUnitBuff = defined =[C]:-1
SetAuctionItem = defined =[C]:-1
}
_ = "Kalanianaole"
unit = "mouseover"
guid = "Player-4648-002C2C0F"
guildName = "Valhalla"
character = {
MainSpec = "-"
Name = "Kalanianaole"
Talents = {
}
OffSpec = "-"
Class = "MAGE"
Level = 60
PaperDollStats = {
}
}
r = 0.250000
g = 0.780000
b = 0.920000
(*temporary) = defined =[C]:-1
(*temporary) = GameTooltip {
0 =
SetText = defined =[C]:-1
SetHyperlink = defined =[C]:-1
SetTradeSkillItem = defined =[C]:-1
hasMoney = 1
comparing = false
Hide = defined =[C]:-1
SetCraftItem = defined =[C]:-1
SetQuestRewardSpell = defined @BootyBayGazette\libs\LibExtraTip\LibExtraTip.lua:419
SetQuestLogRewardSpell = defined @BootyBayGazette\libs\LibExtraTip\LibExtraTip.lua:419
SetShapeshift = defined @BootyBayGazette\libs\LibExtraTip\LibExtraTip.lua:419
ClearLines = defined =[C]:-1
LibExtraTipLeft = {
}
ARKTTD = {
}
Show = defined =[C]:-1
__hasEPGPTooltip = false
SetPetAction = defined @BootyBayGazette\libs\LibExtraTip\LibExtraTip.lua:419
SetUnitDebuff = defined =[C]:-1
SetItemByID = defined =[C]:-1
SetLootItem = defined =[C]:-1
SetQuestItem = defined =[C]:-1
default = 1
SetTrainerService = defined =[C]:-1
numMoneyFrames = 1
TopOverlay = {
}
LibExtraTipRight = {
}
SetInboxItem = defined =[C]:-1
SetBuybackItem = defined =[C]:-1
shoppingTooltips = {
}
ttGradient = {
}
SetMerchantItem = <function

Hmm, I haven't looked at this addon for a while now.

Looking at line 341 it's trying to set some text and a texture string. The line above though it checks if the value exists.

Is this definitely a Guildbook error, what happens if you deactivate other tooltip addons or addons that modify the tooltip, I might have to look at some compatability issues.