For #2275, fix bug for transcode engine config param.

AUTHORS.txt

@@ -79,3 +79,4 @@ CONTRIBUTORS ordered by first contribution.
 * ghostsf<ghost_sf@163.com>
 * xbpeng121<53243357+xbpeng121@users.noreply.github.com>
 * johzzy<hellojinqiang@gmail.com>
+* stone<bluestn@163.com>

trunk/src/app/srs_app_config.cpp

@@ -3925,7 +3925,7 @@ srs_error_t SrsConfig::check_normal_config()
                                 && e != "acodec" && e != "abitrate" && e != "asample_rate" && e != "achannels"
                                 && e != "aparams" && e != "output" && e != "perfile"
                                 && e != "iformat" && e != "oformat") {
-                                return srs_error_new(ERROR_SYSTEM_CONFIG_INVALID, "illegal vhost.transcode.engine.%s of %s", m.c_str(), vhost->arg0().c_str());
+                                return srs_error_new(ERROR_SYSTEM_CONFIG_INVALID, "illegal vhost.transcode.engine.%s of %s", e.c_str(), vhost->arg0().c_str());
                             }
                         }
                     }