Fix config loading for "hugo mod init"

Fix config loading for "hugo mod init"

We have some commands that will continue even if the config loading fails (e.g. because a module can not be found). In Hugo 0.84.0 we introduced a new `_merge` flag that we removed once the configuration was loaded. But we did not do that in error situations, leading to failures in some situations.

This commit fixes that by making sure the configuration is always cleaned before return, even in error situations.

Fixes #8697