[AKS] az aks create: Fix the issue where enabling v1 container storage does not fail if the VM SKU field is left empty (#32109)

Author: nearora-msft

src/azure-cli/azure/cli/command_modules/acs/azurecontainerstorage/_validators.py

@@ -661,7 +661,7 @@ def _validate_nodepools(  # pylint: disable=too-many-branches,too-many-locals
                         'and retry the Azure Container Storage operation.'
                     )
             vm_size = agentpool.get("vm_size")
-            if vm_size is not None:
+            if vm_size is not None and vm_size != "":
                 cpu_value, nvme_enabled = get_vm_sku_details(vm_size.lower())
                 if cpu_value is None or nvme_enabled is None:
                     raise UnknownError(

src/azure-cli/azure/cli/command_modules/acs/managed_cluster_decorator.py

@@ -8825,7 +8825,7 @@ def update_azure_container_storage(self, mc: ManagedCluster) -> ManagedCluster:
             except Exception as ex:
                 raise UnknownError(
                     f"An error occurred while checking the version of Azure Container Storage"
-                    f"extension installed on the cluster: {str(ex)}"
+                    f" extension installed on the cluster: {str(ex)}"
                 ) from ex
 
             disable_azure_container_storage_v1 = disable_azure_container_storage_param is not None and is_container_storage_v1_extension_installed