Crash in src/compiler/types.c:1047

## Reproduction

```c3
import std;
alias Aa = List{Path?};

```

## Compiler Output

```
⚠️ The compiler encountered an unexpected error: "Violated assert: !type_is_optional(ptr_type)".

- Function: type_get_ptr(...)
- Source file: src/compiler/types.c:1047
```

*Exit Code: 1 ([Line on GitHub](https://github.com/c3lang/c3c/blob/master/src/compiler/types.c#L1047))*
