...terface\AddOns\xCT+\libs\LibSink-2.0\LibSink-2.0.lua:253: table index is nil
Count: 2

Call Stack:
[C]: ?
...terface\AddOns\xCT+\libs\LibSink-2.0\LibSink-2.0.lua:253: in function <...terface\AddOns\xCT+\libs\LibSink-2.0\LibSink-2.0.lua:249>
...terface\AddOns\xCT+\libs\LibSink-2.0\LibSink-2.0.lua:262: in function `rescanChannels'
...terface\AddOns\xCT+\libs\LibSink-2.0\LibSink-2.0.lua:264: in main chunk

Interface\AddOns\xCT+\core.lua:1551: attempt to call method 'RegisterSink' (a nil value)
Count: 1

Call Stack:
[C]: in function `RegisterSink'
Interface\AddOns\xCT+\core.lua:1551: in main chunk

There was a small update in a recent WoW release which necessitated a LibSink update.

I've just pushed the new version of that library to the master branch, if you want to manually update it now, or you can wait for dandruff to release the new build on Curse.