This can be reproduced by /reloading while under an override-bar invoking transformation. In particular, I noticed it while doing Song of Wind and Water. Steps were tested with no other addons loaded, but whether this occurs in other vehicle ui states is uncertain.

Message: Interface\FrameXML\RestrictedExecution.lua:397: Call failed: Interface\FrameXML\RestrictedExecution.lua:397: Call failed: Interface\FrameXML\RestrictedExecution.lua:397: Call failed: [string " local state = message..."]:6: attempt to perform arithmetic on a nil value Time: 02/04/16 20:15:55 Count: 1 Stack: [C]: ? Interface\FrameXML\RestrictedExecution.lua:397: in function <Interface\FrameXML\RestrictedExecution.lua:390> (tail call): ? (tail call): ? Interface\FrameXML\SecureHandlers.lua:113: in function <Interface\FrameXML\SecureHandlers.lua:108> [C]: in function 'SetAttribute' Interface\AddOns\Dominos\bars\actionBar.lua:248: in functionUpdateOverrideBar'
Interface\AddOns\Dominos\bars\actionBar.lua:238: in function LoadStateController' Interface\AddOns\Dominos\bars\actionBar.lua:80: in functionNew'
Interface\AddOns\Dominos\bars\actionBar.lua:567: in function Load' Interface\AddOns\Dominos\Dominos.lua:117: in functionLoad'
Interface\AddOns\Dominos\Dominos.lua:53: in function <Interface\AddOns\Dominos\Dominos.lua:51>
(tail call): ?

[string "safecall Dispatcher[1]"]:9: in function <[string "safecall Dispatcher[1]"]:5>
(tail call): ?
...ce\AddOns\Dominos\libs\AceAddon-3.0\AceAddon-3.0.lua:558: in function EnableAddon' ...ce\AddOns\Dominos\libs\AceAddon-3.0\AceAddon-3.0.lua:651: in function <...ce\AddOns\Dominos\libs\AceAddon-3.0\AceAddon-3.0.lua:636> [C]: in functionLoadAddOn'
Interface\FrameXML\UIParent.lua:343: in function UIParentLoadAddOn' Interface\FrameXML\UIParent.lua:422: in functionTimeManager_LoadUI'
Interface\FrameXML\UIParent.lua:923: in function <Interface\FrameXML\UIParent.lua:825>

Locals: (*temporary) = "Call failed: Interface\FrameXML\RestrictedExecution.lua:397: Call failed: Interface\FrameXML\RestrictedExecution.lua:397: Call failed: [string " local state = message..."]:6: attempt to perform arithmetic on a nil value"
`

Can you try 6.2.9 once it's up?
http://www.wowinterface.com/downloads/info9085-Dominos.html

I just did a test in a siege engine in ulduar. I am in the siege engine after talking to the npc brann to start eh encounter. I am not in combat while doing this so maybe that has something to do with something something unsecure /secure calls?!

Edit: Nope went into combat and reloaded to test and it still errored

6.2.9 and got the same error. Even checking to use the blizzard override bar doesn't help.

Of note as well is that with actionbars unchecked in advanced to "show with override UI", they still show. when "use blizzard override action bar" is unchecked.

Error attached for reference:

`4x FrameXML\RestrictedExecution.lua:397: Call failed: FrameXML\RestrictedExecution.lua:397: Call failed: FrameXML\RestrictedExecution.lua:397: Call failed: [string " local state = message..."]:6: attempt to perform arithmetic on a nil value

FrameXML\RestrictedExecution.lua:397: in function <FrameXML\RestrictedExecution.lua:390>
(tail call): ?
(tail call): ?
FrameXML\SecureHandlers.lua:113: in function <FrameXML\SecureHandlers.lua:108>
C: in function SetAttribute' Dominos\bars\actionBar.lua:250: in functionUpdateOverrideBar'
Dominos\bars\actionBar.lua:240: in function LoadStateController' Dominos\bars\actionBar.lua:80: in functionNew'
Dominos\bars\actionBar.lua:569: in function Load' Dominos\Dominos-6.2.9.lua:117: in functionLoad'
Dominos\Dominos-6.2.9.lua:53: in function <Dominos\Dominos.lua:51>
(tail call): ?

[string "safecall Dispatcher[1]"]:9: in function <[string "safecall Dispatcher[1]"]:5>
(tail call): ?
...aceMasque\Libs\AceAddon-3.0\AceAddon-3.0-12.lua:558: in function EnableAddon' ...aceMasque\Libs\AceAddon-3.0\AceAddon-3.0-12.lua:651: in function <...aceMasque\Libs\AceAddon-3.0\AceAddon-3.0.lua:636> [C]: in functionLoadAddOn'
FrameXML\UIParent.lua:343: in function UIParentLoadAddOn' FrameXML\UIParent.lua:366: in functionCombatLog_LoadUI'
FrameXML\UIParent.lua:925: in function <FrameXML\UIParent.lua:825>

Locals:
workingEnv =
ctrlHandle =
pcallFlag = false
LOCAL_Function_Environment_Manager = defined @FrameXML\RestrictedExecution.lua:209
error = defined =C:-1
tostring = defined =C:-1`

Pretty sure this is what is causing the conflict or at least the start of a cascade.

self.header:SetAttribute('state-overridebar', isOverrideBar)

Just to test, I commented out the above with the "use blizzard override action bar " check in options and was able to reload. Now I understand this isn't the solutione because if you uncheck that, it does not swap actionbar 1 to the vehicle ui action buttons but thought I would share this. I'm using this change with the option checked until you find a fix so I don't accidentally reload and throw an error.

I bet it probably works better now :P

I may or may not have forgot to mention it is working now oops :o

Much better thanks ;)

Hurray :)