report bug:type '() => Null' is not a subtype of type '(() => Expression)?' of 'orElse'

[shangguanyanyan]

exception :
type '() => Null' is not a subtype of type '(() => Expression)?' of 'orElse'

package version : ^2.0.0-nullsafety.0

stack:
When the exception was thrown, this was the stack:
#0 ListMixin.firstWhere (dart:collection/list.dart)
#1 declarationsToStyle. (package:flutter_html/src/css_parser.dart:52:62)
#2 _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:397:8)
#3 declarationsToStyle (package:flutter_html/src/css_parser.dart:10:16)
#4 inlineCSSToStyle (package:flutter_html/src/css_parser.dart:85:10)

flutter version:
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 2.0.4, on macOS 11.1 20C69 darwin-x64, locale zh-Hans-CN)
[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.2)
[✓] Xcode - develop for iOS and macOS
[✓] Chrome - develop for the web
[✓] Android Studio (version 4.1)
[✓] IntelliJ IDEA Community Edition (version 2020.2)
[✓] VS Code (version 1.54.3)
[✓] Connected device (2 available)

[tneotia]

This is a known bug and has been fixed on master.

[erickok]

Please try master (or await 2.0.0 release).