[libpeas] Don't use lgi_enter_func if not found

[Garrett Regier <gregier src gnome org>]

commit c280b2e105ea7377a91166db45c19563ad40e5a8
Author: Garrett Regier <garrettregier gmail com>
Date:   Mon Jan 5 11:09:17 2015 -0800

    Don't use lgi_enter_func if not found
    
    Prevents segfault when using an old LGI version.

 loaders/lua5.1/peas-plugin-loader-lua.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/loaders/lua5.1/peas-plugin-loader-lua.c b/loaders/lua5.1/peas-plugin-loader-lua.c
index d5464d0..270a680 100644
--- a/loaders/lua5.1/peas-plugin-loader-lua.c
+++ b/loaders/lua5.1/peas-plugin-loader-lua.c
@@ -547,7 +547,8 @@ peas_plugin_loader_lua_finalize (GObject *object)
   /* Must take the lock as Lua code will run on lua_close
    * and another thread might be running Lua code already
    */
-  priv->lgi_enter_func (priv->lgi_lock);
+  if (priv->lgi_enter_func != NULL)
+    priv->lgi_enter_func (priv->lgi_lock);
 
   g_clear_pointer (&priv->L, (GDestroyNotify) lua_close);