firebase-ios-sdk: Crash via -[FRepo deferredInit]

Environment

• Xcode version: 8.3.3

• Firebase SDK version (from Podfile.lock):

  • Firebase/Auth (4.1.1):
    • Firebase/Core
    • FirebaseAuth (= 4.1.1)
  • Firebase/Core (4.1.1):
    • FirebaseAnalytics (= 4.0.3)
    • FirebaseCore (= 4.0.6)
  • Firebase/Database (4.1.1):
    • Firebase/Core
    • FirebaseDatabase (= 4.0.2)

• Library version: ?

• Firebase Product: database

Problem

I see crashes via Crashlytics with following stack trace:

Fatal Exception: NSInvalidArgumentException
0  CoreFoundation                 0x18d65afe0 __exceptionPreprocess
1  libobjc.A.dylib                0x18c0bc538 objc_exception_throw
2  CoreFoundation                 0x18d661ef4 __methodDescriptionForSelector
3  CoreFoundation                 0x18d65ef54 ___forwarding___
4  CoreFoundation                 0x18d55ad4c _CF_forwarding_prep_0
5  Poloniex                       0x1003cd8dc -[FSnapshotHolder updateSnapshot:withNewSnapshot:]
6  Poloniex                       0x1003c5b70 -[FRepo updateInfo:withValue:]
7  Poloniex                       0x1003c2e48 -[FRepo deferredInit]
8  libdispatch.dylib              0x18c5129e0 _dispatch_call_block_and_release
9  libdispatch.dylib              0x18c5129a0 _dispatch_client_callout
10 libdispatch.dylib              0x18c520ad4 _dispatch_queue_serial_drain
11 libdispatch.dylib              0x18c5162cc _dispatch_queue_invoke
12 libdispatch.dylib              0x18c520fa8 _dispatch_queue_override_invoke
13 libdispatch.dylib              0x18c522a50 _dispatch_root_queue_drain
14 libdispatch.dylib              0x18c5227d0 _dispatch_worker_thread3
15 libsystem_pthread.dylib        0x18c71b100 _pthread_wqthread
16 libsystem_pthread.dylib        0x18c71acac start_wqthread

The origin is always at [FRepo deferredInit]. I do have some bread crumbs (CLS_LOG) in Crashlytics that tell me that the crash happens immediately after app start. It’s a relatively rare crash, however it’s my number one crash in my application.

Steps to reproduce:

I don’t know how to reproduce it, I can only see the crash reports in Crashlytics.