Fix user creation via wf

system/automation/expr_types.go

@@ -31,6 +31,8 @@ func CastToUser(val interface{}) (out *types.User, err error) {
 	switch val := expr.UntypedValue(val).(type) {
 	case *types.User:
 		return val, nil
+	case nil:
+		return &types.User{}, nil
 	default:
 		return nil, fmt.Errorf("unable to cast type %T to %T", val, out)
 	}
@@ -48,6 +50,8 @@ func CastToRole(val interface{}) (out *types.Role, err error) {
 	switch val := expr.UntypedValue(val).(type) {
 	case *types.Role:
 		return val, nil
+	case nil:
+		return &types.Role{}, nil
 	default:
 		return nil, fmt.Errorf("unable to cast type %T to %T", val, out)
 	}
@@ -84,6 +88,8 @@ func CastToTemplateMeta(val interface{}) (out types.TemplateMeta, err error) {
 	switch val := expr.UntypedValue(val).(type) {
 	case types.TemplateMeta:
 		return val, nil
+	case nil:
+		return types.TemplateMeta{}, nil
 	default:
 		return types.TemplateMeta{}, fmt.Errorf("unable to cast type %T to %T", val, out)
 	}
@@ -144,6 +150,8 @@ func CastToQueueMessage(val interface{}) (out *types.QueueMessage, err error) {
 	switch val := expr.UntypedValue(val).(type) {
 	case *types.QueueMessage:
 		return val, nil
+	case nil:
+		return &types.QueueMessage{}, nil
 	default:
 		return &types.QueueMessage{}, fmt.Errorf("unable to cast type %T to %T", val, out)
 	}