[Plugin: Theme-Check] function tc_add_headers() needs to filter, not replace.

Proposed modification as follows …

function tc_add_headers( $extra_headers ) {
-	$extra_headers = array( 'License', 'License URI', 'Template Version' );
+	$extra_headers = array_merge( (array) $extra_headers, array( 'License', 'License URI', 'Template Version' ) );
	return $extra_headers;
}

In short, this will actually filter the data, rather than deciding any thing already caught by a filter is irrelevant and overwriting it.

https://www.ads-software.com/extend/plugins/theme-check/