fix: do not update/sort env vars when nothing changes

When updating an app with an unrelated change, we should not sort the
existing env vars as that can trigger an unexpected build. We simply
return the old env vars if the new envs and to delete is empty.

api/util/apps.go

@@ -73,6 +73,10 @@ func EnvVarsFromMap(env map[string]string) apps.EnvVars {
 }
 
 func UpdateEnvVars(oldEnvs []apps.EnvVar, newEnvs map[string]string, toDelete []string) apps.EnvVars {
+	if len(newEnvs) == 0 && len(toDelete) == 0 {
+		return oldEnvs
+	}
+
 	envMap := map[string]apps.EnvVar{}
 	for _, v := range oldEnvs {
 		envMap[v.Name] = v