tls: tweak clientCertEngine argument parsing

PR-URL: #38900
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

Author: codebytere

lib/internal/tls.js

@@ -305,15 +305,15 @@ function configSecureContext(context, options = {}, name = 'options') {
     }
   }
 
-  if (clientCertEngine !== undefined) {
+  if (typeof clientCertEngine === 'string') {
     if (typeof context.setClientCertEngine !== 'function')
       throw new ERR_CRYPTO_CUSTOM_ENGINE_NOT_SUPPORTED();
-    if (typeof clientCertEngine !== 'string') {
-      throw new ERR_INVALID_ARG_TYPE(`${name}.clientCertEngine`,
-                                     ['string', 'null', 'undefined'],
-                                     clientCertEngine);
-    }
-    context.setClientCertEngine(clientCertEngine);
+    else
+      context.setClientCertEngine(clientCertEngine);
+  } else if (clientCertEngine !== undefined) {
+    throw new ERR_INVALID_ARG_TYPE(`${name}.clientCertEngine`,
+                                   ['string', 'null', 'undefined'],
+                                   clientCertEngine);
   }
 
   if (ticketKeys !== undefined) {