Fix incompatibilities with some null values for PHP 8.1 (#114)

Author: W0rma

src/Negotiation/BaseAccept.php

@@ -112,11 +112,15 @@ public function hasParameter($key)
 
     /**
      *
-     * @param  string $acceptPart
+     * @param  string|null $acceptPart
      * @return array
      */
     private function parseParameters($acceptPart)
     {
+        if ($acceptPart === null) {
+            return ['', []];
+        }
+
         $parts = explode(';', $acceptPart);
         $type  = array_shift($parts);
 

src/Negotiation/LanguageNegotiator.php

@@ -27,8 +27,8 @@ protected function match(AcceptHeader $acceptLanguage, AcceptHeader $priority, $
         $as = $acceptLanguage->getSubPart();
         $ps = $priority->getSubPart();
 
-        $baseEqual = !strcasecmp($ab, $pb);
-        $subEqual  = !strcasecmp($as, $ps);
+        $baseEqual = !strcasecmp((string)$ab, (string)$pb);
+        $subEqual  = !strcasecmp((string)$as, (string)$ps);
 
         if (($ab == '*' || $baseEqual) && ($as === null || $subEqual || null === $ps)) {
             $score = 10 * $baseEqual + $subEqual;