fix: Throw on cart creation when no region exist (#455)

If you try to create a cart without a region in your setup, we should throw a proper error message.

packages/medusa/src/api/routes/store/carts/create-cart.js

@@ -82,6 +82,14 @@ export default async (req, res) => {
       if (!value.region_id) {
         const regionService = req.scope.resolve("regionService")
         const regions = await regionService.withTransaction(manager).list({})
+
+        if (!regions?.length) {
+          throw new MedusaError(
+            MedusaError.Types.INVALID_DATA,
+            `A region is required to create a cart`
+          )
+        }
+
         regionId = regions[0].id
       }