Disable subscribe symbol if end with CNT

QuantConnect.InteractiveBrokersBrokerage/InteractiveBrokersBrokerage.cs

@@ -3636,6 +3636,12 @@ private bool Subscribe(IEnumerable<Symbol> symbols)
 
                             var id = GetNextId();
                             var contract = CreateContract(subscribeSymbol, includeExpired: false);
+                            if (subscribeSymbol.Value.EndsWith("CNT"))
+                            {
+                                Log.Trace($"InteractiveBrokersBrokerage.Subscribe: cause {subscribeSymbol.Value} is cvr, so ignore subscribe request");
+                                continue;
+                            }
+
                             var symbolProperties = _symbolPropertiesDatabase.GetSymbolProperties(subscribeSymbol.ID.Market, subscribeSymbol, subscribeSymbol.SecurityType, Currencies.USD);
                             var priceMagnifier = symbolProperties.PriceMagnifier;
 
@@ -3766,6 +3772,12 @@ private static bool CanSubscribe(Symbol symbol)
                 return false;
             }
 
+            if (symbol.Value.EndsWith("CNT"))
+            {
+                Log.Trace($"InteractiveBrokersBrokerage.CanSubscribe: cause {symbol.Value} is cvr, so ignore get history");
+                return false;
+            }
+
             // Include future options as a special case with no matching market, otherwise
             // our subscriptions are removed without any sort of notice.
             return
@@ -4559,7 +4571,8 @@ private string GetSymbolExchange(SecurityType securityType, string market, strin
         /// <param name="symbol">Symbol to route</param>
         private string GetSymbolExchange(Symbol symbol)
         {
-            return GetSymbolExchange(symbol.SecurityType, symbol.ID.Market, symbol.ID.Symbol);
+            string exchange = GetSymbolExchange(symbol.SecurityType, symbol.ID.Market, symbol.ID.Symbol);
+            return exchange;
         }
 
         /// <summary>