WowAce

The only addons I have running are RatingBuster r365, Bug Grabber, and BugSack and I'm still getting this error on my Druid whenever I mouse over ANY equipment:

RatingBuster\RatingBuster-r365.lua:3427: attempt to compare number with nil
RatingBuster\RatingBuster-r365.lua:3427: in function "func"
RatingBuster\RatingBuster-r365.lua:4393: in function "StatSummary"
RatingBuster\RatingBuster-r365.lua:2727: in function "handler"
libs\LibTipHooker-1.1\LibTipHooker-1.1-16.lua:179: in function <libs\LibTipHooker-1.1\LibTipHooker-1.1.lua:174>
<in C code>
<in C code>
FrameXML\GameTooltip.lua:314: in function <FrameXML\GameTooltip.lua:217>
<in C code>
!MoncaiCompare\!MoncaiCompare-v1.5.4.lua:37: in function <!MoncaiCompare\!MoncaiCompare.lua:35>
<in C code>
Skillet\Skillet-2.33.lua:544: in function <Skillet\Skillet.lua:543>
<in C code>
Altoholic-r123\Tooltip.lua:558: in function <Altoholic\Tooltip.lua:556>
<in C code>
<in C code>
<in C code>
<in C code>
<in C code>
<in C code>
FrameXML\MerchantFrame.lua:452: in function "MerchantItemButton_OnEnter"
<string>:"*:OnEnter":1: in function <string>:"*:OnEnter":1

Locals:
self = <table> {
SetDefaultModuleLibraries = <func> @Ace3\..\AceAddon-3.0.lua:383
Enable = <func> @Ace3\..\AceAddon-3.0.lua:315
RegisterChatCommand = <func> @Ace3\..\AceConsole-3.0.lua:85
EnableModule = <func> @Ace3\..\AceAddon-3.0.lua:348
modules = <table> {}
GetModule = <func> @Ace3\..\AceAddon-3.0.lua:231
IterateEmbeds = <func> @Ace3\..\AceAddon-3.0.lua:458
defaultModuleLibraries = <table> {}
GetStatMod = <func> @..\RatingBuster.lua:2224
UnregisterChatCommand = <func> @Ace3\..\AceConsole-3.0.lua:111
MODIFIER_STATE_CHANGED = <func> @..\RatingBuster.lua:2331
optionsFrames = <table> {}
SplitDoJoin = <func> @..\RatingBuster.lua:2749
Printf = <func> @Ace3\..\AceConsole-3.0.lua:69
OnProfileChanged = <func> @..\RatingBuster.lua:2242
SetDefaultModulePrototype = <func> @Ace3\..\AceAddon-3.0.lua:425
OnProfileReset = <func> @..\RatingBuster.lua:2249
OnInitialize = <func> @..\RatingBuster.lua:2269
baseName = "RatingBuster"
name = "RatingBuster"
Bench = <func> @..\RatingBuster.lua:4585
IsEnabled = <func> @Ace3\..\AceAddon-3.0.lua:467
orderedModules = <table> {}
StatSummary = <func> @..\RatingBuster.lua:4190
DisableModule = <func> @Ace3\..\AceAddon-3.0.lua:366
ProcessText = <func> @..\RatingBuster.lua:2770
Disable = <func> @Ace3\..\AceAddon-3.0.lua:330
ADDON_LOADED = <func> @..\RatingBuster.lua:2346
OnNewProfile = <func> @..\RatingBuster.lua:2259
RegisterMessage = <func> @Ace3\..\CallbackHandler-1.0.lua:118
GetArgs = <func> @Ace3\..\AceConsole-3.0.lua:144
Print = <func> @Ace3\..\AceConsole-3.0.lua:54
ShowConfig = <func> @..\RatingBuster.lua:2176
PLAYER_LEVEL_UP = <func> @..\RatingBuster.lua:2319
OnDisable = <func> @..\RatingBuster.lua:2312
OnEnable = <func> @..\RatingBuster.lua:2298
IsModule = <func> @Ace3\..\AceAddon-3.0.lua:484
db = <table> {}
SetDefaultModuleState = <func> @Ace3\..\AceAddon-3.0.lua:403
UNIT_AURA = <func> @..\RatingBuster.lua:2326
ClearCache = <func> @..\RatingBuster.lua:2227
SetEnabledState = <func> @Ace3\..\AceAddon-3.0.lua:440
SetupOptions = <func> @..\RatingBuster.lua:2147
enabledState = true
date = "2012-09-05"
RegisterEvent = <func> @Ace3\..\CallbackHandler-1.0.lua:118
UnregisterAllMessages = <func> @Ace3\..\CallbackHandler-1.0.lua:202
version = "5.0.4 (r365)"
UnregisterAllEvents = <func> @Ace3\..\CallbackHandler-1.0.lua:202
SendMessage = <func> @Ace3\..\CallbackHandler-1.0.lua:87
IterateModules = <func> @Ace3\..\AceAddon-3.0.lua:453

It's because its trying to calculate Feral Attack Power, but it was removed with 5.0.4

You can fix it by commenting out or removing the part where its calculating Feral Attack Power for Druids, or wait for author to do so.