Minor fix to the update cart

Author: timdesm

src/OminityApiClient.php

@@ -18,7 +18,7 @@ class OminityApiClient
     /**
      * Version of our client.
      */
-    public const CLIENT_VERSION = "1.3.0";
+    public const CLIENT_VERSION = "1.3.1";
 
     /**
      * Endpoint of the remote API.

src/Resources/Commerce/Cart.php

@@ -329,8 +329,8 @@ public function update()
                     return $value !== null;
                 });
             }, $this->items),
-            "billingAddress" => $this->billingAddress ?? null,
-            "shippingAddress" => $this->shippingAddress ?? null,
+            "billingAddress" => $this->billingAddress ?? [],
+            "shippingAddress" => $this->shippingAddress ?? [],
             "promotionCodes" => $this->promotionCodes ?? [],
         ];