Fix Json renderer with empty changes

Signed-off-by: Jack Cherng <[email protected]>

Author: jfcherng

Diff for: src/Renderer/Html/Json.php

@@ -26,12 +26,26 @@ final class Json extends AbstractHtml
      */
     public function render(): string
     {
+        $changes = $this->getChanges();
+
+        if (empty($changes)) {
+            return self::getIdenticalResult();
+        }
+
         return \json_encode(
-            $this->getChanges(),
+            $changes,
             \JSON_UNESCAPED_UNICODE | \JSON_UNESCAPED_SLASHES
         );
     }
 
+    /**
+     * {@inheritdoc}
+     */
+    public static function getIdenticalResult(): string
+    {
+        return '[]';
+    }
+
     /**
      * {@inheritdoc}
      */