Fix TypeError when asset last_modified meta is null

Author: v-Woody

src/Assets/Asset.php

@@ -601,7 +601,7 @@ public function mimeType()
      */
     public function lastModified()
     {
-        return Carbon::createFromTimestamp($this->meta('last_modified'), config('app.timezone'));
+        return Carbon::createFromTimestamp($this->meta('last_modified') ?? 0, config('app.timezone'));
     }
 
     /**

tests/Assets/AssetTest.php

@@ -663,6 +663,22 @@ public function it_gets_last_modified_time()
         $this->assertEquals(Carbon::parse('2017-01-02 14:35:00')->timestamp, $lastModified->timestamp);
     }
 
+    #[Test]
+    public function it_returns_epoch_when_last_modified_meta_is_null()
+    {
+        Storage::fake('test');
+        Storage::disk('test')->put('foo/test.txt', '');
+        Storage::disk('test')->put('foo/.meta/test.txt.yaml', YAML::dump([
+            'data' => [],
+        ]));
+
+        $asset = (new Asset)->container($this->container)->path('foo/test.txt');
+
+        $lastModified = $asset->lastModified();
+        $this->assertInstanceOf(Carbon::class, $lastModified);
+        $this->assertEquals(0, $lastModified->timestamp);
+    }
+
     #[Test]
     public function it_generates_and_clears_meta_caches()
     {