remove defensive null check

[WalterBright]

dmd is full of pointers. If we start adding defensive checks, there would be a lot of clutter. It's better to only check if the pointer being null is legitimate. Otherwise, a seg fault and stack trace are needed to find the actual bug rather than paper it over.

For reference: https://github.com/dlang/dmd/pull/23194/changes

[dlang-bot]

Thanks for your pull request, @WalterBright!

Bugzilla references

Your PR doesn't reference any Bugzilla issue.

If your PR contains non-trivial changes, please reference a Bugzilla issue or create a manual changelog.

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + dmd#23208"

[WalterBright]

Clearly, this was not a defensive piece of code, it was a necessary one.

[dkorpel]

What I meant with "defensive" is that from the rest of the code, a possible null value for the FuncDeclaration parameter was assumed to be possible, so I applied it more consistently. I later added a test case for that code path to make sure it was needed and that it wouldn't regress, which obviously failed when you remove the check in this PR, so it's working!