fix Issue 22779 - druntime: Calling __delete with null pointer-to-struct segfaults

[ibuclaw]

As per the function documentation:

Destroys and then deallocates an object.

In detail, `__delete(x)` returns with no effect if `x` is `null`. Otherwise, it
performs the following actions in sequence:

[dlang-bot]

Thanks for your pull request, @ibuclaw!

Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	22779	critical	druntime: Calling __delete with null pointer-to-struct segfaults

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 "stable + druntime#3745"