add ObjectOrNullWildcard (#21)

README.md

@@ -77,6 +77,7 @@ The library currently supports the following wildcards:
 - DateTimeWildcard
 - DateTimeOrNullWildcard
 - StringWildcard
+- ObjectOrNullWildcard
 
 ### Usage in CI
 When running your tests in Continuous Integration you would possibly want to disable the creation of snapshots.

src/Wildcard/ObjectOrNullWildcard.php

@@ -0,0 +1,42 @@
+<?php
+
+declare(strict_types=1);
+
+namespace KigaRoo\SnapshotTesting\Wildcard;
+
+use InvalidArgumentException;
+use Webmozart\Assert\Assert;
+
+final class ObjectOrNullWildcard implements Wildcard
+{
+    /** @var string */
+    private $path;
+
+    public function __construct(string $path)
+    {
+        $this->path = $path;
+    }
+
+    public function atPath() : string
+    {
+        return $this->path;
+    }
+
+    /**
+     * @param mixed $mixed
+     */
+    public function match($mixed) : bool
+    {
+        if (null === $mixed) {
+            return true;
+        }
+
+        try {
+            Assert::object($mixed);
+
+            return true;
+        } catch (InvalidArgumentException $exception) {
+            return false;
+        }
+    }
+}