Make sure that the user enters a username for cert auth

Author: NeffIsBack

nxc/connection.py

@@ -559,6 +559,9 @@ def login(self):
 
         if self.args.pfx_cert or self.args.pfx_base64 or self.args.cert_pem:
             self.logger.debug("Trying to authenticate using Certificate pfx")
+            if not self.args.username:
+                self.logger.fail("You must specify a username when using certificate authentication")
+                return False
             with sem:
                 # Static DH params because the ones generated by cryptography are considered unsafe by AD for some weird reason
                 dhparams = {