[Auth] Detect if IndexedDB returns an empty array in platform_browser…

…/persistence. (#7825)

Protection from enumerating an empty list in Auth's reading of IndexedDB results, as this causes errors in some macOS and iOS browser runtimes.

This change addresses Issue #7737 which reported an error of `TypeError undefined is not an object (evaluating 'o.fbase_key')`.

.changeset/tiny-lobsters-own.md

@@ -0,0 +1,5 @@
+---
+'@firebase/auth': patch
+---
+
+Protection from enumerating an empty list in Auth's reading of IndexedDB results, as this causes errors in some macOS and iOS browser runtimes.

packages/auth/src/platform_browser/persistence/indexed_db.ts

@@ -369,13 +369,16 @@ class IndexedDBLocalPersistence implements InternalPersistence {
 
     const keys = [];
     const keysInResult = new Set();
-    for (const { fbase_key: key, value } of result) {
-      keysInResult.add(key);
-      if (JSON.stringify(this.localCache[key]) !== JSON.stringify(value)) {
-        this.notifyListeners(key, value as PersistenceValue);
-        keys.push(key);
+    if (result.length !== 0) {
+      for (const { fbase_key: key, value } of result) {
+        keysInResult.add(key);
+        if (JSON.stringify(this.localCache[key]) !== JSON.stringify(value)) {
+          this.notifyListeners(key, value as PersistenceValue);
+          keys.push(key);
+        }
       }
     }
+
     for (const localKey of Object.keys(this.localCache)) {
       if (this.localCache[localKey] && !keysInResult.has(localKey)) {
         // Deleted