[Bug]: Custom error parsing problem

### Describe the issue:

An error is returned by Slither's parser on: a custom error that includes an array whose length is specified using a constant literal.

### Code example to reproduce the issue:

```solidity
pragma solidity ^0.8.4;

uint256 constant MAX = 1000;
error BadError(
uint32[MAX] y
);

contract VendingMachine {
}
```

### Version:

0.9.2

### Relevant log output:

```shell
( is not valid for find_variable
````
```