Clear cipher list on server creation, fix crash (#5171)

The cipher list values were not initialized to NULL appropriately for the
BearSSL::WiFiClientSecure() constructor called by the Server object.
This caused a crash as a random value was free'd when conecting to the
SSL server object.

libraries/ESP8266WiFi/src/WiFiClientSecureBearSSL.cpp

@@ -116,6 +116,8 @@ WiFiClientSecure::~WiFiClientSecure() {
 WiFiClientSecure::WiFiClientSecure(ClientContext* client,
                                      const BearSSLX509List *chain, const BearSSLPrivateKey *sk,
                                      int iobuf_in_size, int iobuf_out_size, const BearSSLX509List *client_CA_ta) {
+  _cipher_list = NULL;
+  _cipher_cnt = 0;
   _clear();
   _clearAuthenticationSettings();
   _iobuf_in_size = iobuf_in_size;
@@ -133,6 +135,8 @@ WiFiClientSecure::WiFiClientSecure(ClientContext *client,
                                      const BearSSLX509List *chain,
                                      unsigned cert_issuer_key_type, const BearSSLPrivateKey *sk,
                                      int iobuf_in_size, int iobuf_out_size, const BearSSLX509List *client_CA_ta) {
+  _cipher_list = NULL;
+  _cipher_cnt = 0;
   _clear();
   _clearAuthenticationSettings();
   _iobuf_in_size = iobuf_in_size;