do not call preg_match() on null

Author: xabbuh

Request.php

@@ -1502,7 +1502,7 @@ public function isMethodCacheable()
     public function getProtocolVersion()
     {
         if ($this->isFromTrustedProxy()) {
-            preg_match('~^(HTTP/)?([1-9]\.[0-9]) ~', $this->headers->get('Via'), $matches);
+            preg_match('~^(HTTP/)?([1-9]\.[0-9]) ~', $this->headers->get('Via') ?? '', $matches);
 
             if ($matches) {
                 return 'HTTP/'.$matches[2];

Tests/RequestTest.php

@@ -2230,17 +2230,22 @@ public function testProtocolVersion($serverProtocol, $trustedProxy, $via, $expec
         $request = new Request();
         $request->server->set('SERVER_PROTOCOL', $serverProtocol);
         $request->server->set('REMOTE_ADDR', '1.1.1.1');
-        $request->headers->set('Via', $via);
+
+        if (null !== $via) {
+            $request->headers->set('Via', $via);
+        }
 
         $this->assertSame($expected, $request->getProtocolVersion());
     }
 
     public function protocolVersionProvider()
     {
         return [
-            'untrusted without via' => ['HTTP/2.0', false, '', 'HTTP/2.0'],
+            'untrusted with empty via' => ['HTTP/2.0', false, '', 'HTTP/2.0'],
+            'untrusted without via' => ['HTTP/2.0', false, null, 'HTTP/2.0'],
             'untrusted with via' => ['HTTP/2.0', false, '1.0 fred, 1.1 nowhere.com (Apache/1.1)', 'HTTP/2.0'],
-            'trusted without via' => ['HTTP/2.0', true, '', 'HTTP/2.0'],
+            'trusted with empty via' => ['HTTP/2.0', true, '', 'HTTP/2.0'],
+            'trusted without via' => ['HTTP/2.0', true, null, 'HTTP/2.0'],
             'trusted with via' => ['HTTP/2.0', true, '1.0 fred, 1.1 nowhere.com (Apache/1.1)', 'HTTP/1.0'],
             'trusted with via and protocol name' => ['HTTP/2.0', true, 'HTTP/1.0 fred, HTTP/1.1 nowhere.com (Apache/1.1)', 'HTTP/1.0'],
             'trusted with broken via' => ['HTTP/2.0', true, 'HTTP/1^0 foo', 'HTTP/2.0'],