Read from new storage in aflags

Bug: 324436145
Test: adb shell aflags list --use-new-storage
Change-Id: Ib615e25bc0bc7f2b0362e286a45ce40ebf21f92d
diff --git a/tools/aconfig/aflags/src/main.rs b/tools/aconfig/aflags/src/main.rs
index 810f2e3..6d76fd0 100644
--- a/tools/aconfig/aflags/src/main.rs
+++ b/tools/aconfig/aflags/src/main.rs
@@ -286,7 +286,9 @@
     let cli = Cli::parse();
     let output = match cli.command {
         Command::List { use_new_storage: true, container } => {
-            list(FlagSourceType::AconfigStorage, container).map(Some)
+            list(FlagSourceType::AconfigStorage, container)
+                .map_err(|_| anyhow!("storage may not be enabled"))
+                .map(Some)
         }
         Command::List { use_new_storage: false, container } => {
             list(FlagSourceType::DeviceConfig, container).map(Some)