Defining optional globals doesn't trigger nil check warning

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### How are you using the lua-language-server?

Visual Studio Code Extension (sumneko.lua)

### Which OS are you using?

Windows

### What is the issue affecting?

Type Checking

### Expected Behaviour

I have some code that runs in different environments that have different global variables available.

For example, environment1 may have a global table C_GameRules available with a function in it. environment2 does not have the global available.

I'm trying to write a meta file that makes this optional nature of this global available:

```
---@meta

---@type table?
C_GameRules = nil

---@return boolean
function C_GameRules.IsHardcoreActive() end
```

I've also tried to define a class, no change in behavior

### Actual Behaviour

`C_GameRules.IsHardcoreActive()` does not trigger a need-nil-check warning, but the type of C_GameRules gets shown as `table?`

### Reproduction steps

see above

### Additional Notes

i don't want the inner field as nilable, environment 1 has "C_GameRules" as global available and the function is guaranteed to be in there, environment 2 has the global set to nil

### Log File

_No response_

Riproduci il report nella Visual Studio Code Extension usando la dichiarazione del meta-file Lua mostrata e analizza le diagnosi del controllo dei tipi per C_GameRules.IsHardcoreActive(). Il lavoro è completato quando un elemento globale opzionale produce un avviso di controllo di nil, mentre la sua funzione interna rimane non nullable.

Scritto dal modello di indicizzazione a partire dal testo della issue.