.jr will no longer fail if the user isn't in the database yet, fixes #399

src/NadekoBot/Services/Currency/CurrencyService.cs

@@ -88,6 +88,9 @@ public sealed class CurrencyService : ICurrencyService, INService
         long amount,
         TxData txData)
     {
+        if (amount == 0)
+            return true;
+        
         var wallet = await GetWalletAsync(userId);
         var result = await wallet.Take(amount, txData);
         if(result)