Null dev_extension throws error

[gilnobrega]

Hey, I am not sure if this is intentional or not but leaving the default line

  dev_extension: # optional, by default undefined, allows to specify command option to use extension

in environment_config.yaml throws an exception when running dart run environment_config:generate:

type 'Null' is not a subtype of type 'String'

However clearing this line fixes this issue.

[TatsuUkraine]

Hi. Thanks for bringing this issue. I will update type checks