93x OmniBar\Options-Options.lua:108: Usage: NonEmptySpell:ContinueOnLoad(callbackFunction)
[string "=[C]"]: in function error' [string "@FrameXML\ObjectAPI\Spell.lua"]:51: in function ContinueOnSpellLoad'
[string "@omnibar\Options-Options.lua"]:108: in function <OmniBar\Options.lua:53>
[string "@omnibar\Options-Options.lua"]:557: in function AddBarToOptions' [string "@OmniBar\OmniBar-v10.8.lua"]:104: in function <OmniBar\OmniBar.lua:70> [string "=[C]"]: ? [string "@Bartender4\libs\AceAddon-3.0\AceAddon-3.0-13.lua"]:70: in function <Bartender4\libs\AceAddon-3.0\AceAddon-3.0.lua:65> [string "@Bartender4\libs\AceAddon-3.0\AceAddon-3.0-13.lua"]:527: in function EnableAddon'
[string "@bartender4\libs\AceAddon-3.0\AceAddon-3.0-13.lua"]:630: in function <Bartender4\libs\AceAddon-3.0\AceAddon-3.0.lua:615>

I made a pull request for the fix, but in the meantime here is what to change, and a link to the download:

Delete this on line 107 in Options.lua:

local s = Spell:CreateFromSpellID(spellID)
s:ContinueOnSpellLoad(function()
	descriptions[spellID] = s:GetSpellDescription()
end

Replace with this:
descriptions[spellID] = GetSpellDescription(spellID)

Or download here: OmniBar.zip

The twitch app won't update until the owner of the addon includes the fix. For now you have to do it manually.

To install it yourself:
Extract OmniBar.zip into your addon folder. Typically C:\Program Files (x86)\World of Warcraft\_retail_\Interface\AddOns\