Exception in thread "Thread-5"

[kbence0429]

Hi!
I created a minecraft launcher, but when I tried to start the game, I got this error message:

Exception in thread "Thread-5" java.lang.NullPointerException
at java.lang.ProcessBuilder.start(ProcessBuilder.java:1012)
at fr.theshark34.openlauncherlib.external.ExternalLauncher.launch(ExternalLauncher.java:155)
at me.bence.hu.Launcher.launch(Launcher.java:50)
at me.bence.hu.LauncherPanel$1.run(LauncherPanel.java:171)

Code: https://pastebin.com/41qz4NUQ
Minecraft version: Vanilla 1.16.5

Could someone help me?

Regards,
Bence