Fix Memcached version extraction (#222)

## Summary
- adjust Memcached version detection to ignore empty or sentinel values
returned by the Memcached extension and normalise the first valid
version string
- align the Memcached detection unit test with the updated extraction
logic

## Testing
- vendor/bin/phpstan analyse --memory-limit=1G
- vendor/bin/phpunit *(fails: missing WordPress test library in the test
environment)*
- vendor/bin/phpcs *(fails: PHPCompatibilityWP sniff not available in
the current PHPCS setup)*

------
https://chatgpt.com/codex/tasks/task_b_690450140924832185f70e05e56468d7

Author: javiercasares

wpvulnerability-general.php

@@ -912,6 +912,26 @@ function wpvulnerability_detect_memcached() {
 	$version = null;
 
 	// First method: use the Memcached extension of PHP.
+		if ( class_exists( 'Memcached' ) ) {
+			$memcached = new Memcached();
+			try {
+
+				$version_info = $memcached->getVersion();
+
+				if ( is_array( $version_info ) ) {
+					foreach ( $version_info as $reported_version ) {
+						$reported_version = (string) $reported_version;
+
+						if ( '' === $reported_version || '255.255.255' === $reported_version ) {
+							continue;
+						}
+
+						if ( preg_match( '/-(\d+)$/', $reported_version, $suffix_matches ) ) {
+							$reported_version = preg_replace( '/-(\d+)$/', '.' . $suffix_matches[1], $reported_version );
+						}
+
+						$version = $reported_version;
+						break;
 	if ( class_exists( 'Memcached' ) ) {
 		$memcached = new Memcached();
 		try {
@@ -975,12 +995,11 @@ function wpvulnerability_detect_memcached() {
 						}
 					}
 				}
+			} catch ( MemcachedException $e ) {
+				// There is the PHP extension, but no memcached.
+				unset( $memcached );
 			}
-		} catch ( MemcachedException $e ) {
-			// There is the PHP extension, but no memcached.
-			unset( $memcached );
 		}
-	}
 
 	if ( empty( $version ) && class_exists( 'Memcache' ) ) {
 		try {