[BUG] <p>&nbsp;</p> does not create empty space from 3.0.0-beta.2

[mkucharski17]

Describe the bug:
<p>&nbsp;</p> should create space, but starting from version 3.0.0-beta.2 it is ignored. It works properly in version 3.0.0-beta.1

HTML to reproduce the issue:
<p>Paragraph before nbsp<\p><p>&nbsp;<p/><p>Paragraph after nbsp<\p>

Html widget configuration:

        Html(
              data:
                  "<p>Paragraph before nbsp<\p><p>&nbsp;<p/><p>Paragraph after nbsp<\p>",
              style: {
                'p': Style(margin: Margins.all(0)),
              },
            ),

Expected behavior:
It should create empty space.

Screenshots:

Screen using version 3.0.0-beta.2	Screen using version 3.0.0-beta.1

Device details and Flutter/Dart/flutter_html versions:

Flutter 3.22.2 • channel stable • https://github.com/flutter/flutter.git
Framework • revision 761747bfc5 (3 miesiące temu) • 2024-06-05 22:15:13 +0200
Engine • revision edd8546116
Tools • Dart 3.4.3 • DevTools 2.34.3

[Albert221]

Currently the whitespace.dart file removes the &nbsp treating it as a whitespace, and then removes the now-empty p element:

flutter_html/lib/src/processing/whitespace.dart

Lines 16 to 17 in 79ec194

	tree = _processBlockWhitespace(tree);
	tree = _removeEmptyElements(tree);

That's not consistent with how browsers treat such paragraphs. An empty paragraph with a non-breakable space is often used by WYSIWYG editors in CMSes for empty spaces.