[firebase_messaging] Flutter throws NoSuchMethod error when hot restarting (Please read description)

[ThinkDigitalSoftware]

Error thrown is NoSuchMethodError: The method 'add' was called on null. Receiver: null Tried calling: add(Instance of 'QuerySnapshot'):

I don't know why the error is happening, but I have traced down the reason. I'm assuming that my device never deregisters as an observer before it's hot restarted and it contributes to the issue. The attached video can explain the issue better than I can. Please ask for clarification as I'm unable to duplicate it since I don't understand it fully enough.
Video
In cloud_firestore-0.9.7/lib/src/firestore.dart

class Firestore {
  Firestore({FirebaseApp app}) : app = app ?? FirebaseApp.instance {
    if (_initialized) return;
    channel.setMethodCallHandler((MethodCall call) async {
      if (call.method == 'QuerySnapshot') {
        final QuerySnapshot snapshot = QuerySnapshot._(call.arguments, this);

       // THIS IS WHERE THE ERROR OCCURS👇🏾
        _queryObservers[call.arguments['handle']].add(snapshot);
      } else if (call.method == 'DocumentSnapshot') {
        final DocumentSnapshot snapshot = DocumentSnapshot._(
          call.arguments['path'],
          _asStringKeyedMap(call.arguments['data']),
          this,
        );

Variables:
call.arguments['handle'] -> 7

_queryObservers (I just realized that this list starts at a higher number after I hot restart). This must be the cause.

[iapicca]

Hi @ThinkDigitalSoftware
could you please provide your flutter doctor -v
and your flutter run --verbose.
Thank you

[ThinkDigitalSoftware]

Sorry, this was some time ago, my version has changed since then.

[iapicca]

Hi @ThinkDigitalSoftware
given your last message I feel safe to close this issue,
if you disagree please write in the comments
and I will reopen it.
Thank you
#125