aws/resources: Befor importing 'aws_iam_user_group_membership' check …

…grups names

If there is no groups we cannot import this resources so we should skip it

aws/resources.go

@@ -1093,6 +1093,12 @@ func iamUserGroupMemberships(ctx context.Context, a *aws, resourceType string, f
 		return nil, err
 	}
 
+	// If the user has no Groups then we do not need to proceed
+	// or TF will return an error of malformed ID
+	if len(groupNames) == 0 {
+		return nil, nil
+	}
+
 	resources := make([]provider.Resource, 0)
 	for _, un := range userNames {
 		// The format expected by TF is <user-name>/<group-name1>/...