I get the same issue every time I try to start TotalFinder after upgrading to Mojave on my mid-2015 MBPr.
Note that TotalFinder works perfectly on my mid-2014 MBPr after upgrading to Mojave.
EDIT 5 minutes later:
I found the solution here:
sudo tccutil reset AppleEvents
osascript -e "tell application \"Finder\" to «event BATFinit»"