noreturn parameter allows null pointer to be "called"

```D
void main() {
	void function(noreturn) fun;
	noreturn bar;
	fun(bar);
}
```
With DMD 2.112.0, this program compiles and runs to completion. It should not. I expect to see either an assertion (preferably) or a segfault, not skipping the function call entirely.

GCC and LDC assert and segfault, respectively.