Core: fixed default log initialization.

The ngx_log_insert() function may invalidate pointer passed to it,
so make sure to don't use it after the ngx_log_insert() call.

src/core/ngx_log.c

diff --git a/src/core/ngx_log.c b/src/core/ngx_log.c
index 375d52f..005d9ff 100644
--- a/src/core/ngx_log.c
+++ b/src/core/ngx_log.c
@@ -387,20 +387,22 @@
             return NGX_ERROR;
         }
 
-        log->log_level = NGX_LOG_ERR;
-        ngx_log_insert(&cycle->new_log, log);
-
     } else {
         /* no error logs at all */
         log = &cycle->new_log;
-        log->log_level = NGX_LOG_ERR;
     }
 
+    log->log_level = NGX_LOG_ERR;
+
     log->file = ngx_conf_open_file(cycle, &error_log);
     if (log->file == NULL) {
         return NGX_ERROR;
     }
 
+    if (log != &cycle->new_log) {
+        ngx_log_insert(&cycle->new_log, log);
+    }
+
     return NGX_OK;
 }