[Bug]: Reference variable has type `None` when overriding a variable name

### Describe the issue:

When we print IR for the following source code:
```
pragma solidity ^0.8.13;

struct A {
uint256 z;
}

contract MyTest {
A a;

function test() external {
uint a = a.z;
}
}
```

The generated IR does not correctly type the variable `REF_0` as `int`. Instead, it has the type `None`:
```
INFO:Printers:Contract MyTest
Function MyTest.test() (*)
Expression: a = a.z
IRs:
REF_0(None) -> a.z
a(uint256) := REF_0(None)
```

### Code example to reproduce the issue:
```
pragma solidity ^0.8.13;

struct A {
uint256 z;
}

contract MyTest {
A a;

function test() external {
uint a = a.z;
}
}
```
### Version:

0.9.6

### Relevant log output:

```shell
INFO:Printers:Contract MyTest
Function MyTest.test() (*)
Expression: a = a.z
IRs:
REF_0(None) -> a.z
a(uint256) := REF_0(None)
```