fix warning: int is not a pointer.

Author: tadd

ext/mysql2/client.c

@@ -286,7 +286,7 @@ static VALUE rb_connect(VALUE self, VALUE user, VALUE pass, VALUE host, VALUE po
 
   args.host = NIL_P(host) ? NULL : StringValuePtr(host);
   args.unix_socket = NIL_P(socket) ? NULL : StringValuePtr(socket);
-  args.port = NIL_P(port) ? NULL : NUM2INT(port);
+  args.port = NIL_P(port) ? 0 : NUM2INT(port);
   args.user = NIL_P(user) ? NULL : StringValuePtr(user);
   args.passwd = NIL_P(pass) ? NULL : StringValuePtr(pass);
   args.db = NIL_P(database) ? NULL : StringValuePtr(database);