Fix crash on Flutter Web

[rostopira]

No description provided.

[WahdanZ]

Could you show us how to use the sdk with flutter web ?

[rostopira]

@WahdanZ it's basically straightforward with some caveats

flutter channel master
flutter upgrade --force
flutter run -d chrome

LiveQuery not working currently (I'm working on it)
And for CoreStore I'm using stub (WIP as well)
SecurityContext is unsupported, throws on constructor, just don't use it
Also be aware, that it's doesn't support dart:io and will throw even on Platform.isAndroid
You can still use it like this:

if (identical(0, 0.0)) {
  // I'm Flutter Web
  // Use 'dart:html' package
} else if (Platform.isAndroid) {
  // Use 'dart:io'
}

[rostopira]

As I already said, it's WIP, I will provide more PR's for flutter web soon, just part by part, not all at once