I am having the same issue. I got frozen on that screen, so I redid the level. But after getting all the way past the final cutscene the game just gets stuck on a black screen with music playing. Did you find any fix yet?
The issue I had with the game freezing after the first phase of the fight was fixed, however it appears that I also have the same issue now, where after the cutscene I get a black screen and music plays, like you. The best option is to just wait for another hotfix to be released.
Bugs like this are to be expected when a game has a major update though, I'm sure the developers will release another hotfix to fix the issue soon, so I'm just gonna wait for it. The Nightclub boss fight isn't that challenging so I don't mind having to replay it whenever it bugs out like this.