Opened game & keep getting this error. Help?

2x Interface/AddOns/Blizzard_Flyout/Flyout.lua:96: attempt to index field 'popup' (a nil value)
[C]: ?
[C]: ?
[Interface/AddOns/Blizzard_FrameXML/SecureHandlers.lua]:40: in function <...nterface/AddOns/Blizzard_FrameXML/SecureHandlers.lua:39>
[Interface/AddOns/Blizzard_FrameXML/SecureHandlers.lua]:268: in function <...nterface/AddOns/Blizzard_FrameXML/SecureHandlers.lua:263>
[C]: ?
[Interface/AddOns/Blizzard_FrameXML/SecureHandlers.lua]:296: in function <...nterface/AddOns/Blizzard_FrameXML/SecureHandlers.lua:279>
[tail call]: ?

Locals: