Crash in OID Request

We're using AppAuth (0.9.1) through CocoaPods. We are using it indirectly through GTMAppAuth.

We've been having the following crash in our app for a while. It looks like the OIDTokenRequest clientID is nil. By following the trace, it looks like it's coming from clientID:_lastAuthorizationResponse.request.clientID in OIDAuthState.m.

Fatal Exception: NSInvalidArgumentException
0  CoreFoundation                 0x18162b164 __exceptionPreprocess
1  libobjc.A.dylib                0x180874528 objc_exception_throw
2  CoreFoundation                 0x1815c3c9c _CFArgv
3  CoreFoundation                 0x1814f6eec -[__NSArrayM insertObject:atIndex:]
4  HelloWorld                     0x102852760 -[OIDURLQueryComponent addParameter:value:] (OIDURLQueryComponent.m:99)
5  HelloWorld                     0x102851060 -[OIDTokenRequest URLRequest] (OIDTokenRequest.m:284)
6  HelloWorld                     0x102847dc8 +[OIDAuthorizationService performTokenRequest:callback:] (OIDAuthorizationService.m:263)
7  HelloWorld                     0x10284afcc -[OIDAuthState performActionWithFreshTokens:additionalRefreshParameters:] (OIDAuthState.m:500)
8  HelloWorld                     0x1029fe75c -[GTMAppAuthFetcherAuthorization authorizeRequestArgs:] (GTMAppAuthFetcherAuthorization.m:329)
9  HelloWorld                     0x1029fe688 -[GTMAppAuthFetcherAuthorization authorizeRequest:delegate:didFinishSelector:] (GTMAppAuthFetcherAuthorization.m:306)
10 HelloWorld                     0x102a0c778 -[GTMSessionFetcher authorizeRequest] (GTMSessionFetcher.m:1577)
11 HelloWorld                     0x102a08a1c -[GTMSessionFetcher beginFetchMayDelay:mayAuthorize:] (GTMSessionFetcher.m:733)
12 HelloWorld                     0x102a308b4 -[GTLRService fetchObjectWithURL:objectClass:bodyObject:dataToPost:ETag:httpMethod:mayAuthorize:completionHandler:executingQuery:ticket:] (GTLRService.m:836)
13 HelloWorld                     0x102a320c4 -[GTLRService fetchObjectWithURL:objectClass:bodyObject:ETag:httpMethod:mayAuthorize:completionHandler:executingQuery:ticket:] (GTLRService.m:1096)
14 HelloWorld                     0x102a3641c -[GTLRService executeQuery:completionHandler:] (GTLRService.m:2213)
15 HelloWorld                     0x102c634bc -[GoogleDocsEngine loadContent:] (GoogleDocsEngine.m:296)
16 HelloWorld                     0x102c766b0 -[TGLExportDirectoryPickerViewController viewDidAppear:] (TGLExportDirectoryPickerViewController.m:73)
17 UIKit                          0x18abfe588 -[UIViewController _setViewAppearState:isAnimating:]
18 UIKit                          0x18abfeaf4 -[UIViewController _endAppearanceTransition:]
19 UIKit                          0x18aca3dbc -[UINavigationController navigationTransitionView:didEndTransition:fromView:toView:]
20 UIKit                          0x18ad6a81c __49-[UINavigationController _startCustomTransition:]_block_invoke
21 UIKit                          0x18acf687c -[_UIViewControllerTransitionContext completeTransition:]
22 UIKit                          0x18ae3ac04 __53-[_UINavigationParallaxTransition animateTransition:]_block_invoke.124
23 UIKit                          0x18ac1e188 -[UIViewAnimationBlockDelegate _didEndBlockAnimation:finished:context:]
24 UIKit                          0x18ac1dafc -[UIViewAnimationState sendDelegateAnimationDidStop:finished:]
25 UIKit                          0x18ac1d808 -[UIViewAnimationState animationDidStop:finished:]
26 UIKit                          0x18ac1d8a8 -[UIViewAnimationState animationDidStop:finished:]
27 QuartzCore                     0x18567edc4 CA::Layer::run_animation_callbacks(void*)
28 libdispatch.dylib              0x180faaa14 _dispatch_client_callout
29 libdispatch.dylib              0x180fb7698 _dispatch_main_queue_callback_4CF$VARIANT$mp
30 CoreFoundation                 0x1815d3344 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__
31 CoreFoundation                 0x1815d0f20 __CFRunLoopRun
32 CoreFoundation                 0x1814f0c58 CFRunLoopRunSpecific
33 GraphicsServices               0x18339cf84 GSEventRunModal
34 UIKit                          0x18ac495c4 UIApplicationMain
35 HelloWorld                     0x1024aff2c main (main.m:10)
36 libdyld.dylib                  0x18101056c start

Thanks!

Start with OIDAuthState.m at performActionWithFreshTokens:additionalRefreshParameters:, then inspect OIDTokenRequest.m and OIDURLQueryComponent.m at the stack-trace locations. Reproduce the refresh-token path through GTMAppAuth and determine why the clientID reaches the token request as nil. Done means the crash cause is identified and the affected path has regression coverage.