Flutter iOS RevenueCat uncaught exception 'NSInternalInconsistencyException'

I got this error in console:

[Purchases] - INFO: There is no singleton instance. Make sure you configure Purchases before trying to get the default instance.
*** Assertion failure in +[RCCommonFunctionality getPurchaserInfoWithCompletionBlock:], RCCommonFunctionality.m:118
*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'You must call setup first.'
*** First throw call stack:
(0x1a0379654 0x1a009bbcc 0x1a027c6ec 0x1a06c216c 0x1032908ac 0x1032cdf9c 0x1032cc0d4 0x105c3ae30 0x1053ef758 0x1056d58b4 0x1053f90ec 0x1053fb818 0x1a02f8134 0x1a02f7e50 0x1a02f752c 0x1a02f253c 0x1a02f1ba8 0x1aa461344 0x1a442d3e4 0x102c4069c 0x1a01798f0)
libc++abi.dylib: terminating with uncaught exception of type NSException
* thread #1, queue = 'com.apple.main-thread', stop reason = signal SIGABRT
    frame #0: 0x00000001a016ed88 libsystem_kernel.dylib`__pthread_kill + 8
libsystem_kernel.dylib`__pthread_kill:
->  0x1a016ed88 <+8>:  b.lo   0x1a016eda4               ; <+36>
    0x1a016ed8c <+12>: stp    x29, x30, [sp, #-0x10]!
    0x1a016ed90 <+16>: mov    x29, sp
    0x1a016ed94 <+20>: bl     0x1a014dad0               ; cerror_nocancel
Target 0: (Runner) stopped.
Lost connection to device.

However, this is an intermittent problem (i.e: doesn't always happen). In fact, I have setup the Purchases instance at startup (i.e: immediately after user is authenticated and I got the UID):

 await Purchases.setDebugLogsEnabled(isDebugEnabled);
 await Purchases.setup(kRevenueCatApiKey, appUserId: uid);

Is there anything I missed? (but most of the time it works)

Solution

I found the problem. So whenever getPurchaserInfo is called, but if Purchaser.setup hasn't finish processing, then it will fire this exception. Thanks to the comment by @Cesar above.

In my case, I found the problem was because:

I had two Blocs that handles IAP and Business logic respectively.
The IAP calls Purchases.setup as soon as the user is authenticated. Then at the main screen, the Business logic will check validity of local data with server by doing getPurchaserInfo.
The problem comes when the internet connection is not great and getPurchaserInfo gets fired by Business logic bloc before Purchases.setup finish processing.

So the solution I did was by making sure that Business logic bloc starts initializing once IAP bloc done with Purchases.setup. Such as placing them in an async function that awaits for each process.