src/BearSSLClient.cpp: fix _ecSign

The client can specify its own _ecSign function since commit
996778e as well as its own certificate
since commit 874c6b0
The goal was to allow the user to use ArduinoBearSSL without the ECCX08
(for example with an (e)SIM applet compliant to the new GSMA IoT SAFE
standard).

However, these two functions don't work because
br_ssl_client_set_single_ec is not called if _ecKey.xlen is set to 0 so
fix this latest issue

Signed-off-by: Fabrice Fontaine <[email protected]>

Author: ffontaine

Diff for: src/BearSSLClient.cpp

@@ -301,7 +301,7 @@ int BearSSLClient::connectSSL(const char* host)
   br_x509_minimal_set_ecdsa(&_xc, br_ssl_engine_get_ec(&_sc.eng), br_ssl_engine_get_ecdsa(&_sc.eng));
 
   // enable client auth
-  if (_ecCert.data_len && _ecKey.xlen) {
+  if (_ecCert.data_len) {
     br_ssl_client_set_single_ec(&_sc, &_ecCert, 1, &_ecKey, BR_KEYTYPE_KEYX | BR_KEYTYPE_SIGN, BR_KEYTYPE_EC, br_ec_get_default(), _ecSign);
   }