this crash is described here: https://github.com/FirebaseExtended/flutterfire/issues/2390

FlutterFire-CloudFirestorePlugin

E/AndroidRuntime(18109): java.lang.NullPointerException: Attempt to invoke virtual method 'void io.flutter.plugin.common.MethodChannel.invokeMethod(java.lang.String, java.lang.Object)' on a null object reference
E/AndroidRuntime(18109): 	at io.flutter.plugins.firebase.cloudfirestore.CloudFirestorePlugin$EventObserver.onEvent(CloudFirestorePlugin.java:451)
E/AndroidRuntime(18109): 	at io.flutter.plugins.firebase.cloudfirestore.CloudFirestorePlugin$EventObserver.onEvent(CloudFirestorePlugin.java:433)
E/AndroidRuntime(18109): 	at com.google.firebase.firestore.Query.lambda$addSnapshotListenerInternal$2(com.google.firebase:firebase-firestore@@21.3.0:1025)
E/AndroidRuntime(18109): 	at com.google.firebase.firestore.Query$$Lambda$3.onEvent(Unknown Source:6)
E/AndroidRuntime(18109): 	at com.google.firebase.firestore.core.AsyncEventListener.lambda$onEvent$0(com.google.firebase:firebase-firestore@@21.3.0:42)
E/AndroidRuntime(18109): 	at com.google.firebase.firestore.core.AsyncEventListener$$Lambda$1.run(Unknown Source:6)
E/AndroidRuntime(18109): 	at android.os.Handler.handleCallback(Handler.java:883)
E/AndroidRuntime(18109): 	at android.os.Handler.dispatchMessage(Handler.java:100)
E/AndroidRuntime(18109): 	at android.os.Looper.loop(Looper.java:214)
E/AndroidRuntime(18109): 	at android.app.ActivityThread.main(ActivityThread.java:7356)
E/AndroidRuntime(18109): 	at java.lang.reflect.Method.invoke(Native Method)
E/AndroidRuntime(18109): 	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
E/AndroidRuntime(18109): 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
I/Process (18109): Sending signal. PID: 18109 SIG: 9