[1.0.0-pre.1]Using Style(before: "!") will raise error

[canisterism]

Hi, I really like this package and thank you committers to create such great package.
Here I report unexpected behavior that seems a bug.

Environment

• flutter_html: ^1.0.0-pre.1

$ flutter doctor
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, v1.12.13+hotfix.5, on Mac OS X 10.14.5 18F132, locale en-JP)
[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
[✓] Xcode - develop for iOS and macOS (Xcode 11.3.1)
[✓] Android Studio (version 3.5)
[✓] VS Code (version 1.43.2)
[✓] Connected device (1 available)

• No issues found!

Steps to reproduce

Here's code to reproduce.

Html(
  data: '<span class="another-bullet-point">aaa</span>',
  style: {
    ".another-bullet-point": Style(after: "!"),
  }
)

Expected Result

I wanted to alternate <li>' s bullet point with before: "!".

(In the first place, I wanted to change bullet point of <li>, from ・ to !, however it's not supported though)

So, I expected to show screen like below.

! aaa

Actual Result

App raises error. Here's track trace below.

════════ Exception caught by widgets library ═══════════════════════════════════
The following NoSuchMethodError was thrown building HtmlParser(dirty):
The getter 'height' was called on null.
Receiver: null
Tried calling: height

The relevant error-causing widget was
    Html 
lib/main.dart:92
When the exception was thrown, this was the stack
#0      Object.noSuchMethod  (dart:core-patch/object_patch.dart:53:5)
#1      HtmlParser._collapseMargins 
package:flutter_html/html_parser.dart:505
#2      List.forEach  (dart:core-patch/growable_array.dart:285:8)
#3      HtmlParser._collapseMargins 
package:flutter_html/html_parser.dart:512
#4      List.forEach  (dart:core-patch/growable_array.dart:285:8)

Visual Proof (screenshots, videos, text)

Screenshot when exception raises:

screen:

[Sub6Resources]

Thank you. This is a very helpful error report. We will work on fixing this.

[canisterism]

Thank you for response. I'm looking forward to fixing it!

[ryan-berger]

@canisterism This issue should be fixed if you upgrade to v1.0.0.