Just got to this point as well and its happening to me. Tried multiple times changing some of the dialogue along the way to see if it would stop the bug but I still get. I now have beat that boss in nightmare mode 3 times just to get stuck after it. Very dissappointing. Might just have to side with the templars :/
Edit: Mashing the skip button as suggested above worked. Have to do boss fight again though.
