FirebaseAnalytics sessionID / sessionIDWithCompletion returning 0 occasionally without error?

### Description

Hi there - been fuzzing the iOS platform in react-native-firebase with a new massively parallel test run feature in CI, and I've noticed that occasionally we get zeros back for analytics session ID - though that can't be a valid session can it?

We don't return a value if the error object is defined, so it appears this is an erroneous return value.

Heard internally @ Invertase that this turns up on FlutterFire occasionally as well, causing a CI run to false-negative and I assume would impact users as well. Plural of anecdote is anecdata not data, but that gives me a little more confidence this is a problem.

It only happens occasionally so it is likely something race-y in firebase-ios-sdk and I'm curious if

a) a zero session id with no error object is ever a valid combination?
b) if anyone else has seen this or I'm blazing trail here and it needs more investigation

I'm going to bend a zero return value to an error at the react-native-firebase layer as I assume the answer to item A above is "nope, that shouldn't happen..."

Our implementation is dead-simple:

https://github.com/invertase/react-native-firebase/blob/f8d5a9d5cc811d2601e0fc0f32b58ffdd98cfff2/packages/analytics/ios/RNFBAnalytics/RNFBAnalyticsModule.m#L128-L139

My latest test run where I saw this - failed with this zero sessionId / no-error combo 2 out of 30 runs

https://github.com/invertase/react-native-firebase/actions/runs/17225729926/job/48869796447#step:25:3873

### Reproducing the issue

_No response_

### Firebase SDK Version

12.1.0

### Xcode Version

16.4.0

### Installation Method

CocoaPods

### Firebase Product(s)

Analytics

### Targeted Platforms

iOS

### Relevant Log Output

```shell

```

### If using Swift Package Manager, the project's Package.resolved

Expand Package.resolved snippet

```json

Replace this line with the contents of your Package.resolved.

```

### If using CocoaPods, the project's Podfile.lock

The Podfile.lock was erroring on issue creation because it is too large.

Have no fear, it's generally available on github though :-)

https://github.com/invertase/react-native-firebase/blob/f8d5a9d5cc811d2601e0fc0f32b58ffdd98cfff2/tests/ios/Podfile.lock