Symfony version(s) affected: 4.2

Description
I did this:

framework:
    ide: '%env(IDE_PATH)%'

and this:

xdebug.file_link_format = "phpstorm://open?url=file://%f&line=%l"

and got this:

I'm not sure what I expected to happen. I didn't expect an exception by overriding an environment variable though.

How to reproduce
The good news is, there's a reproducer app.
The bad news is you have to set xdebug.file_link_format to get the error.

Possible Solution
¯\_(ツ)_/¯