Fix NPE in AccountManagerService.

Test: atest AccountManagerServiceTest
Bug: 243969466
Change-Id: I59ad96dfd6894dda21d2a8c86b18ee88dc7f7a00

services/core/java/com/android/server/accounts/AccountManagerService.java

@@ -1870,7 +1870,7 @@ public class AccountManagerService
                     }
                     if (accounts.accountsDb.findAllDeAccounts().size() > 100) {
                         Log.w(TAG, "insertAccountIntoDatabase: " + account.toSafeString()
-                                + ", skipping since more than 50 accounts on device exist");
+                                + ", skipping since more than 100 accounts on device exist");
                         return false;
                     }
                     long accountId = accounts.accountsDb.insertCeAccount(account, password);
@@ -3520,10 +3520,10 @@ public class AccountManagerService
 
                 @Override
                 protected String toDebugString(long now) {
-                    String requiredFeaturesStr = TextUtils.join(",", requiredFeatures);
                     return super.toDebugString(now) + ", startAddAccountSession" + ", accountType "
                             + accountType + ", requiredFeatures "
-                            + (requiredFeatures != null ? requiredFeaturesStr : null);
+                            + (requiredFeatures != null
+                                ? TextUtils.join(",", requiredFeatures) : "null");
                 }
             }.bind();
         } finally {