Nullability warnings are not solved by null checking

**Bicep version**
v0.43.8

**Describe the bug**
When a module accepts a nullable object as a parameter, Bicep still gives a nullability warning when dotting into that object even after checking that it is not null. For example, `vnet.name` and `vnet.resourceGroupName` both give warnings here when they shouldn't:

```bicep
resource vnetResource 'Microsoft.Network/virtualNetworks@2024-01-01' existing = if (vnet != null) {
name: vnet.name // The value of type "null | { name: string, resourceGroupName: string }" may be null at the start of the deployment
scope: resourceGroup(vnet.resourceGroupName) // The value of type "null | { name: string, resourceGroupName: string }" may be null at the start of the deployment
}
```

I'd expect the `if (vnet != null) ` check to make the nullability warnings go away.

**To Reproduce**

```bicep
type Foo = {
bar: string
}

param foo Foo?

resource a 'Microsoft.Network/virtualNetworks@2024-01-01' existing = if (foo != null) {
name: foo.foo // The value of type "null | { name: string, resourceGroupName: string }" may be null at the start of the deployment
}
```

Reproduce the warning with the nullable Foo parameter and the `if (foo != null)` resource condition shown in the issue. Trace the compiler's nullability analysis for property access inside conditional resource bodies. Done means accesses such as `foo.foo`, `vnet.name`, and `vnet.resourceGroupName` no longer warn after the corresponding null check, with regression coverage for the reported examples.

Written by the indexing model from the issue text.