Avoid PHP warnings about undefined array keys when sanitizing malform…

…ed PEMs (#556)

* Avoid PHP warnings about undefined indexes when sanitizing malformed PEMs
* Add test for loading invalid PEM key

A new test function was added in ECKeysTest.php to handle cases of loading invalid PEM keys. An InvalidArgumentException is expected to be thrown with a specific error message when an invalid private PEM key is loaded.

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Co-authored-by: Florent Morselli <florent.morselli@spomky-labs.com>

KeyManagement/KeyConverter/KeyConverter.php

@@ -365,7 +365,11 @@ private static function getCurve(string $oid): string
      */
     private static function sanitizePEM(string &$pem): void
     {
-        preg_match_all('#(-.*-)#', $pem, $matches, PREG_PATTERN_ORDER);
+        $number = preg_match_all('#(-.*-)#', $pem, $matches, PREG_PATTERN_ORDER);
+        if ($number !== 2) {
+            throw new InvalidArgumentException('Unable to load the key');
+        }
+
         $ciphertext = preg_replace('#-.*-|\r|\n| #', '', $pem);
 
         $pem = $matches[0][0] . PHP_EOL;