Fix improper detection of the domain by property.

Author: kagg-design

WPForms/Sniffs/PHP/ValidateDomainSniff.php

@@ -187,6 +187,7 @@ private function getExpectedDomain( $phpcsFile ) {
 	 */
 	private function findDomainByProperty( $filePath ) {
 
+		$filePath      = ltrim( $filePath, DIRECTORY_SEPARATOR );
 		$currentDomain = '';
 		$currentPath   = '';