fix: gracefully handle missing tag for syncing

cli/recipe/release.go

@@ -127,6 +127,7 @@ your SSH keys configured on your account.
 func getImageVersions(recipe recipe.Recipe) (map[string]string, error) {
 	var services = make(map[string]string)
 
+	missingTag := false
 	for _, service := range recipe.Config.Services {
 		if service.Image == "" {
 			continue
@@ -146,12 +147,19 @@ func getImageVersions(recipe recipe.Recipe) (map[string]string, error) {
 		case reference.NamedTagged:
 			tag = img.(reference.NamedTagged).Tag()
 		case reference.Named:
-			return services, fmt.Errorf("%s service is missing image tag?", path)
+			if service.Name == "app" {
+				missingTag = true
+			}
+			continue
 		}
 
 		services[path] = tag
 	}
 
+	if missingTag {
+		return services, fmt.Errorf("app service is missing image tag?")
+	}
+
 	return services, nil
 }