Can no longer reference sub environment variables from the base environment

### Expected Behavior

Sub Environment variables used to work when referenced in the Base Environment.

### Actual Behavior

The reference links are now broken and Insomnia cannot find the variables

### Reproduction Steps

1. Create a Sub Environment and create a variable called var1
2. Go to Base Environment and create a new variable that references var1 as `_.var1`.

### Is there an existing issue for this?

- [X] I have searched the [issue tracker](https://www.github.com/Kong/insomnia/issues) for this problem.

### Additional Information

_No response_

### Insomnia Version

2023.5.3

### What operating system are you using?

macOS

### Operating System Version

macOS Monterey 12.2.1 and Ventura 13.5

### Installation method

downloaded from insomnia.rest

### Last Known Working Insomnia version

2023.4.0

Reproduce the regression in Insomnia 2023.5.3 by referencing a Sub Environment variable from the Base Environment as `_.var1`, then trace environment-variable resolution. Done means the Base Environment resolves the Sub Environment variable again, matching the behavior in version 2023.4.0.

Written by the indexing model from the issue text.