Refresh 반복, int is not subtype of double

이건 무슨 에러인가요?

Refresh를 여러번 반복하면 자꾸 발생합니다.

그리고 자꾸 int is not subtype of double 에러도 났다가 안났다가 하네요

════════ Exception caught by widgets library

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The following NoSuchMethodError was thrown building StreamBuilder<Object>(dirty, state: _StreamBuilderBaseState<Object, AsyncSnapshot<Object>>#3c54d):

The getter 'pollution' was called on null.

Receiver: null

Tried calling: pollution

The relevant error-causing widget was: 

  StreamBuilder<Object> file:///D:/Project/Flutter/flutter_mise_app/flutter_mise_app/lib/main.dart:40:16

When the exception was thrown, this was the stack: 

#0      Object.noSuchMethod (dart:core-patch/object_patch.dart:53:5)

#1      _MainState.getMappedData (package:fluttermiseapp/main.dart:148:47)

#2      _MainState.buildPadding (package:fluttermiseapp/main.dart:72:30)

#3      _MainState.build.<anonymous closure> (package:fluttermiseapp/main.dart:45:24)

#4      StreamBuilder.build (package:flutter/src/widgets/async.dart:509:81)

...