additional nil check

Co-authored-by: Matthew Frahry <[email protected]>

azurerm/helpers/azure/kusto.go

@@ -45,7 +45,7 @@ func SchemaKustoIdentity() *schema.Schema {
 }
 
 func ExpandKustoIdentity(input []interface{}) *kusto.Identity {
-	if len(input) == 0 {
+	if len(input) == 0 || input[0] == nil {
 		return nil
 	}
 	identity := input[0].(map[string]interface{})