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Unity editor version: 2019.2.17f1
Firebase Unity SDK version: 6.13
Source you installed the SDK (.unitypackage or Unity Package Manager): .unitypackage
Firebase plugins in use (Auth, Database, etc.): Database, Storage, Auth, Analytics
Additional SDKs you are using (Facebook, AdMob, etc.): None
Platform you are using the Unity editor on (Mac, Windows, or Linux): Mac
Platform you are targeting (iOS, Android, and/or desktop): iOS
Scripting Runtime (Mono, and/or IL2CPP):IL2CPP

Please describe the issue here:

This isn't for every snapshot, this is for an operation whereas I iterate over a snapshot of keys and get snapshots for those keys. Everything is async, running through Action callback. The crash seems to occur wherever the snapshot is accessed after whatever bug occurs, doesn't matter if its snapshot.HasChild, snapshot.Child().Value, or snapshot.Child().Exists.

`Obtained 6 stack frames.
#0 0x00000159763274 in firebase::database::internal::GetVariantValue(firebase::Variant const*)
#1 0x0000015975f888 in firebase::database::internal::VariantGetChild(firebase::Variant const*, firebase::Path const&)
#2 0x0000015974898a in firebase::database::internal::DataSnapshotInternal::HasChild(char const*) const
#3 0x000001596fdbb0 in Firebase_Database_CSharp_InternalDataSnapshot_HasChild__SWIG_0
#4 0x00000154419c33 in (wrapper managed-to-native) Firebase.Database.Internal.DatabaseInternalPINVOKE:InternalDataSnapshot_HasChild__SWIG_0 (System.Runtime.InteropServices.HandleRef,string) {0x7fd9358a6970} + 0x163 (0x154419ad0 0x154419db9) [0x17941bc80 - Unity Child Domain]
#5 0x007fd933934500 in (Unknown)
Launching bug reporter'

What's the issue repro rate? (eg 100%, 1/5 etc)
100% on iOS