Check for valid session object before calling get_customer_id in Cart Route (#52410)

* Check for valid session object before calling get_customer_id in Cart Route

* Add changefile(s) from automation for the following project(s): woocommerce

* Harden get_cart_token function to make sure the cart is loaded before we access the session

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Co-authored-by: github-actions <github-actions@github.com>

plugins/woocommerce/changelog/52410-fix-52326-jwt-error-when-no-session

@@ -0,0 +1,4 @@
+Significance: patch
+Type: fix
+
+Make sure session exists before calling its functions in the Cart StoreApi route

plugins/woocommerce/src/StoreApi/Routes/V1/AbstractCartRoute.php

@@ -188,6 +188,13 @@ abstract class AbstractCartRoute extends AbstractRoute {
 	 * @return string
 	 */
 	protected function get_cart_token() {
+		// Ensure cart is loaded.
+		$this->cart_controller->load_cart();
+
+		if ( ! wc()->session ) {
+			return null;
+		}
+
 		return JsonWebToken::create(
 			[
 				'user_id' => wc()->session->get_customer_id(),