[glib] Check for (GIConv)-1 instead of NULL.

[Ignacio Casal Quinteiro <icq src gnome org>]

commit ab3a79e2c9be13aea5b2ce0980f3a641c5ed081d
Author: Ignacio Casal Quinteiro <icq gnome org>
Date:   Sun Nov 21 21:20:44 2010 +0100

    Check for (GIConv)-1 instead of NULL.

 gio/gcharsetconverter.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gio/gcharsetconverter.c b/gio/gcharsetconverter.c
index ea60437..3ec621f 100644
--- a/gio/gcharsetconverter.c
+++ b/gio/gcharsetconverter.c
@@ -451,7 +451,7 @@ g_charset_converter_initable_init (GInitable *initable,
   conv->iconv =
     g_iconv_open (conv->to, conv->from);
 
-  if (conv->iconv == NULL)
+  if (conv->iconv == (GIConv)-1)
     {
       if (errno == EINVAL)
 	g_set_error (error, G_IO_ERROR, G_IO_ERROR_NOT_SUPPORTED,