safeguards for monero subaddress list (#3242)

cw_monero/lib/monero_subaddress_list.dart

@@ -34,8 +34,9 @@ abstract class MoneroSubaddressListBase with Store {
     try {
       _isUpdating = true;
       refresh(accountIndex: accountIndex);
+      final newAddrs = await getAll();
       subaddresses.clear();
-      subaddresses.addAll(await getAll());
+      subaddresses.addAll(newAddrs);
       _isUpdating = false;
     } catch (e) {
       _isUpdating = false;

lib/view_model/wallet_address_list/wallet_address_list_view_model.dart

@@ -214,7 +214,7 @@ abstract class WalletAddressListViewModelBase extends WalletChangeListenerViewMo
     final addressList = ObservableList<ListItem>();
 
     if (wallet.type == WalletType.monero) {
-      final primaryAddress = monero!.getSubaddressList(wallet).subaddresses.first;
+      final primaryAddress = monero!.getSubaddressList(wallet).subaddresses.firstOrNull;
       final addressItems = monero!.getSubaddressList(wallet).subaddresses.map((subaddress) {
         final isPrimary = subaddress == primaryAddress;
 

lib/view_model/wallet_address_list/wallet_address_util.dart

@@ -25,9 +25,16 @@ Future<void> createNewAddress(WalletBase wallet, String label) async {
     await monero!
         .getSubaddressList(wallet)
         .addSubaddress(wallet, accountIndex: monero!.getCurrentAccount(wallet).id, label: label);
-    final addr = await monero!
+    final subaddressList = await monero!
         .getSubaddressList(wallet)
-        .subaddresses
+        .subaddresses;
+    if(subaddressList.isEmpty) {
+      // this shouldn't happen, we just added an addr.
+      // somehow, it happened once in prod regardless.
+      // we just return instead of crashing, user can press the button again ig
+      return;
+    }
+    final addr = subaddressList
         .first
         .address; // first because the order is reversed
     wallet.walletAddresses.manualAddresses.add(addr);