fix retarded code (#744)

Content.Server/Store/Systems/StoreSystem.Ui.cs

@@ -297,6 +297,9 @@ public sealed partial class StoreSystem
     /// </remarks>
     private void OnRequestWithdraw(EntityUid uid, StoreComponent component, StoreRequestWithdrawMessage msg)
     {
+        if (msg.Amount <= 0)
+            return;
+
         //make sure we have enough cash in the bank and we actually support this currency
         if (!component.Balance.TryGetValue(msg.Currency, out var currentAmount) || currentAmount < msg.Amount)
             return;
@@ -320,7 +323,8 @@ public sealed partial class StoreSystem
             var cashId = proto.Cash[value];
             var amountToSpawn = (int) MathF.Floor((float) (amountRemaining / value));
             var ents = _stack.SpawnMultiple(cashId, amountToSpawn, coordinates);
-            _hands.PickupOrDrop(buyer, ents.First());
+            if (ents.FirstOrDefault() is {} ent)
+                _hands.PickupOrDrop(buyer, ent);
             amountRemaining -= value * amountToSpawn;
         }