[cloud_firestore] Crash "An error occurred while executing doInBackground()" about flutterfire

[creativecreatorormaybenot]

I looked at where doInBackground is used, I can say that I use Transaction#set/update/get but never delete. I have no idea what part of my Dart code is causing these issues.

Luckily this crash happens a lot in Play Store pre-launch reports and seeing that this happens right after start up when first loading content (UI is already displayed), I think it can only be Transaction#set.

Update: I suppose what I described here could be #79.

The `transaction.set` calls I am looking at use `FieldValue.serverTimestamp()`, so maybe it has something to do with multiple of these transactions piling up? Reason I say this: Sometimes, I see my app crash when there is bad connection and I try to perform an action like "incrementing a value", which is a transaction, and if the bad connection causes the transaction to not update the value (immediately), I will trigger it again manually, and again and after some of these actions "pile" up, the app will crash - so I imagine that this issue is **similar** or that one of these stack traces actually is exactly what I described.

Most likely it is what I can see in pre-launch recordings: right after start up with Transaction#set's that have FieldValue.serverTimestamp().

I cannot replicate it in debug mode (probably because I have a stable connection?) and it does not happen to every user, i.e. just a few percent.

[creativecreatorormaybenot]

Another "version" of this crash:

Fatal Exception: java.lang.RuntimeException: An error occurred while executing doInBackground()
       at android.os.AsyncTask$3.done + 353(AsyncTask.java:353)
       at java.util.concurrent.FutureTask.finishCompletion + 383(FutureTask.java:383)
       at java.util.concurrent.FutureTask.setException + 252(FutureTask.java:252)
       at java.util.concurrent.FutureTask.run + 271(FutureTask.java:271)
       at android.os.AsyncTask$SerialExecutor$1.run + 245(AsyncTask.java:245)
       at java.util.concurrent.ThreadPoolExecutor.runWorker + 1162(ThreadPoolExecutor.java:1162)
       at java.util.concurrent.ThreadPoolExecutor$Worker.run + 636(ThreadPoolExecutor.java:636)
       at java.lang.Thread.run + 764(Thread.java:764)

Caused by java.lang.NullPointerException: Attempt to invoke virtual method 'com.google.firebase.firestore.ak com.google.firebase.firestore.ak.a(com.google.firebase.firestore.d, java.lang.Object)' on a null object reference
       at io.flutter.plugins.firebase.cloudfirestore.CloudFirestorePlugin$7.doInBackground + 20(CloudFirestorePlugin.java:20)
       at io.flutter.plugins.firebase.cloudfirestore.CloudFirestorePlugin$7.doInBackground + 2(CloudFirestorePlugin.java:2)
       at android.os.AsyncTask$2.call + 333(AsyncTask.java:333)
       at java.util.concurrent.FutureTask.run + 266(FutureTask.java:266)
       at android.os.AsyncTask$SerialExecutor$1.run + 245(AsyncTask.java:245)
       at java.util.concurrent.ThreadPoolExecutor.runWorker + 1162(ThreadPoolExecutor.java:1162)
       at java.util.concurrent.ThreadPoolExecutor$Worker.run + 636(ThreadPoolExecutor.java:636)
       at java.lang.Thread.run + 764(Thread.java:764)

I think adding all the devices it occured on is not useful here, but I can do that if it helps.