Describe the bug:
Since I upgraded from 3.0.0-alpha6 to beta2, I have an issue on old Safari versions. The Html widget renders as a gray area and I see in the console the error:

FormatException: Illegal RegExp pattern (SyntaxError: Invalid regular expression: invalid group specifier name)
(?<=\n) *

HTML to reproduce the issue:
Any HTML content

Html widget configuration:
No specific configuration

Expected behavior:
HTML properly rendered, instead of gray area.

Screenshots:

Device details and Flutter/Dart/flutter_html versions:
iOS 12.5.5, flutter_html 3.0.0-beta.2

Stacktrace/Logcat

FormatException: Illegal RegExp pattern (SyntaxError: Invalid regular expression: invalid group specifier name)
(?<=\n) *

Additional info:

A picture of a cute animal (not mandatory but encouraged)