#1241 Segmentation fault with enabled shuffle

[Maxim Starodubcev]

1. Run qmmp with qsui interface
2. Enable shuffle playlist (i use grouped playlist but i dont check it with other settings/ui combinations)
3. Close qmmp
4. Run qmmp again

Result: Segmentation fault

I fixed this for me by adding null pointer initialization for PlayState *playState in src/qmmpui/playlistmodel.cpp:PlayListModelPrivate

private:
...
    PlayState *playState = nullptr; /*!< Current playing state (Normal or Shuffle) */
...

[Maxim Starodubcev]

I forgot to specify versions: 2.4.1 and 2.4.2.