[Bug] readme.txt parser fails if there are empty lines between headers

[Ryokuhi]

Describe the bug
In case there is an empty line between headers in the readme.txt file, the parser parses correctly only headers before the empty line: other headers are incorrectly parsed as short description and the short description is not parsed at all.

To Reproduce

1. Edit the readme.txt file of a theme by adding an empty line between headers. An easy way to catch the bug is to add the empty line before the License header.
2. Run the Theme Sniffer: you'll get the two following warnings (since the parser cannot parse the License header, the license property is empty).
   • No matching license critera could be determined from: !
   • Unable to determine License URI with an invalid License supplied in readme.txt!
3. Remove the empty line between headers in the readme.txt file.
4. Run the Theme Sniffer again: the warnings disappear.

Expected behavior
I'm not aware of guidelines preventing developers from adding line breaks between headers.
As such, I would expect that adding one or more empty lines between headers doesn't cause parsing errors.

Environment

• OS: Windows
• Browser: both Chrome and Firefox
• Version: both 1.1.2 and development
• PHP Version: 7.4
• WP Version: development

Additional context
The following snippet shows that the parser has a few lines of code intended to allow line breaks between headers.

theme-sniffer/src/sniffs/readme/class-parser.php

Lines 233 to 238 in 1d6c852

	// Some plugins have line-breaks within the headers.
	if ( empty( $line ) ) {
	break;
	} else {
	continue;
	}

The cause of this issue is that the break and continue controls are switched: header parsing should continue if the line is empty and it should break if the line is not empty, but it is not a header either (i.e. if it doesn't contain a colon).