Thanks for pointing this out. It seems that $USER is usually set but might not be depending on how you start your session. After doing some research, it seems the portable (posix compliant) way is to spawn a subshell running id -u -n, and I like to stay posix compliant 
Should fix it: https://github.com/EndeavourOS-Community-Editions/worm/commit/e3f73e7d27b1ab67c2bba00fba7781f06446088d