Invidtui crashes if MPV window is closed

Config: Up-to-date Arch with invidtui from aur/invidtui-bin
Steps to reproduce: launch a video with 'V', mpv starts playing video in own window, close window
Actual result: invidtui crashes; screws up the terminal most of the time on crash; sometimes leaves behind $XDG_HOME/.config/invidtui/socket on crash
Expected result: detects mpv exit and handles it cleanly

Discovered because mpv can't be terminated normally via keybind as per #41