Infinite loop with links inside table headers and GitHubWeb extension

[isoos]

The following markdown has a table header with a link:

| Configuration Name | Description (from [microsoft docs](https://docs.microsoft.com/en-us/uwp/schemas/appxpackage/appxmanifestschema/schema-root "microsoft docs")) | Default Value (value type) | Required |
| ------------ | ------------ | ------------ |
|  display_name | A friendly name that can be displayed to users. | MyApp (string) | No |

Running with dart run markdown --extension-set GitHubWeb causes an infinite loop. Removing the link from the header renders jus fine.