mail: Fix yahoo login for existing users

app/ui/legacy/src/main/java/com/fsck/k9/activity/setup/accountmanager/EeloAccountCreator.java

@@ -98,8 +98,8 @@ public class EeloAccountCreator {
         android.accounts.Account[] openIdAccounts =
             accountManager.getAccountsByType(accountType);
         for (android.accounts.Account openIdAccount : openIdAccounts) {
-            String emailId =
-                accountManager.getUserData(openIdAccount, AccountManagerConstants.ACCOUNT_EMAIL_ADDRESS_KEY);
+            final String emailId = getEmailId(accountManager, openIdAccount);
+
             if (isInvalidEmail(emailId)) {
                 continue;
             }
@@ -149,7 +149,8 @@ public class EeloAccountCreator {
         android.accounts.Account[] eeloAccounts =
             accountManager.getAccountsByType(AccountManagerConstants.EELO_ACCOUNT_TYPE);
         for (android.accounts.Account eeloAccount : eeloAccounts) {
-            String emailId = accountManager.getUserData(eeloAccount, AccountManagerConstants.ACCOUNT_EMAIL_ADDRESS_KEY);
+            final String emailId = getEmailId(accountManager, eeloAccount);
+
             if (isInvalidEmail(emailId)) {
                 continue;
             }
@@ -176,6 +177,16 @@ public class EeloAccountCreator {
         }
     }
 
+    private static String getEmailId(AccountManager accountManager, android.accounts.Account account) {
+        String emailId = accountManager.getUserData(account, AccountManagerConstants.ACCOUNT_EMAIL_ADDRESS_KEY);
+
+        if (emailId == null || emailId.equals("null") || emailId.isBlank()) {
+            return account.name;
+        }
+
+        return emailId;
+    }
+
     @RequiresApi(api = VERSION_CODES.N)
     private static void deleteIncompleteAccounts(List<Account> accounts, BackgroundAccountRemover accountRemover) {
         accounts.stream().filter(account -> !account.isFinishedSetup())