fix: a tag should not style as link if href is not provided

[Sub6Resources]

Fixes #1092

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@2ffa1dd). Click here to learn what that means.
Patch coverage: 100.00% of modified lines in pull request are covered.

❗ Current head 4cf38e6 differs from pull request most recent head b7facb5. Consider uploading reports for the commit b7facb5 to get more accurate results

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #1265   +/-   ##
=========================================
  Coverage          ?   58.07%           
=========================================
  Files             ?       36           
  Lines             ?     2607           
  Branches          ?        0           
=========================================
  Hits              ?     1514           
  Misses            ?     1093           
  Partials          ?        0           

Impacted Files	Coverage Δ
lib/src/builtins/interactive_element_builtin.dart	94.59% <100.00%> (ø)
lib/src/builtins/styled_element_builtin.dart	96.81% <100.00%> (ø)
lib/src/processing/relative_sizes.dart	70.00% <100.00%> (ø)

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.