Make sure a serialized DumpDataCollector can be unserialized

Signed-off-by: Alexander M. Turek <me@derrabus.de>

Author: derrabus

DataCollector/DumpDataCollector.php

@@ -31,7 +31,7 @@
  */
 class DumpDataCollector extends DataCollector implements DataDumperInterface
 {
-    private ?Stopwatch $stopwatch;
+    private ?Stopwatch $stopwatch = null;
     private string|FileLinkFormatter|false $fileLinkFormat;
     private int $dataCount = 0;
     private bool $isCollected = true;

Tests/DataCollector/DumpDataCollectorTest.php

@@ -54,7 +54,11 @@ public function testDump()
 
         $this->assertStringMatchesFormat('%a;a:%d:{i:0;a:5:{s:4:"data";%c:39:"Symfony\Component\VarDumper\Cloner\Data":%a', serialize($collector));
         $this->assertSame(0, $collector->getDumpsCount());
-        $this->assertSame("O:60:\"Symfony\Component\HttpKernel\DataCollector\DumpDataCollector\":1:{s:7:\"\0*\0data\";a:2:{i:0;b:0;i:1;s:5:\"UTF-8\";}}", serialize($collector));
+
+        $serialized = serialize($collector);
+        $this->assertSame("O:60:\"Symfony\Component\HttpKernel\DataCollector\DumpDataCollector\":1:{s:7:\"\0*\0data\";a:2:{i:0;b:0;i:1;s:5:\"UTF-8\";}}", $serialized);
+
+        $this->assertInstanceOf(DumpDataCollector::class, unserialize($serialized));
     }
 
     public function testDumpWithServerConnection()