pleezer allows resource exhaustion through uncollected hook script processes

pleezer is a headless Deezer Connect player. Hook scripts in pleezer can be triggered by various events like track changes and playback state changes. In versions before 0.16.0, these scripts were spawned without proper process cleanup, leaving zombie processes in the system's process table. Even during normal usage, every track change and playback event would leave behind zombie processes. This leads to inevitable resource exhaustion over time as the system's process table fills up, eventually preventing new processes from being created. The issue is exacerbated if events occur rapidly, whether through normal use (e.g., skipping through a playlist) or potential manipulation of the Deezer Connect protocol traffic. This issue has been fixed in version 0.16.0.