fixed PY-15045 Newly created cell evaluation

do not remove cell from update map on empty payload. On payload is executed even on plain code evaluation

python/ipnb/src/org/jetbrains/plugins/ipnb/configuration/IpnbConnectionManager.java

@@ -177,7 +177,6 @@ public final class IpnbConnectionManager implements ProjectComponent {
           if (!myUpdateMap.containsKey(parentMessageId)) return;
           final IpnbCodePanel cell = myUpdateMap.remove(parentMessageId);
           if (payload != null) {
-            //noinspection unchecked
             cell.updatePanel(payload, null);
           }
         }

python/ipnb/src/org/jetbrains/plugins/ipnb/protocol/IpnbConnection.java

@@ -462,9 +462,6 @@ public class IpnbConnection {
             myListener.onPayload(payload.text, parentHeader.getMessageId());
           }
         }
-        else {
-          myListener.onPayload(null, parentHeader.getMessageId());
-        }
       }
       else if ("pyerr".equals(messageType) || "error".equals(messageType)) {
         final PyErrContent content = gson.fromJson(msg.getContent(), PyErrContent.class);