Environment fallback not working in .env file.

[GerbenLimburg]

Given system variable SYS_VAR=the_value when set: and an .env file: Some__env__var=${SYS_VAR:-fallback}

Using docker-compose v1.29.2, this results in either: Some__env__var=the_value when SYS_VAR has a value or Some__env__var=fallback when SYS_VAR is not set or is empty.

In docker compose v2.2.3 this results in Some__env__var=the_value:-fallback when SYS_VAR has a value or Some__env__var=:-fallback when SYS_VAR is not set or is empty.

To me, the behaviour in v2.2.3 is unexpected.