EthernetClient BUG

[TingRuazhang]

void EthernetClient::stop()
{
if (_tcp_client == NULL) {
return;
}

// close tcp connection if not closed yet
if (status() != TCP_CLOSING) {
tcp_connection_close(_tcp_client->pcb, _tcp_client);
}
mem_free(_tcp_client);
}

In this function, memefree (_tcp_cient);, After release, the _tcp_cient was not set to NULL, which caused an exception when TCPClient was reconnected. After adding it, it worked normally. Please fix this issue

[fpistm]

Hi @q1098401179
feel free to provide a PR it's a community project.