Put this file on the root of your sd card, overwriting the old one:
https://github.com/fincs/new-hbmenu/releases/download/v2.0.0/boot.3dsx. Many people forget this step. Also, you didn't replace your music app. What it does is it loads up the hbl instead of 3ds sound until you reboot the 3ds. Lastly, for future reference on gbatemp, please make your thread title relevant to your question. "Homebrew launcher crash" helps alot more than "plss help". It also helps if you could go into more detail such as your 3ds firmware and how exactly you got the error.