[libmediaart] extract: Incorrect inverse variable check for media_art_set()

[Martyn James Russell <mr src gnome org>]

commit 1c6cfd6728502020a01f9cfab6733bac311298e3
Author: Martyn Russell <martyn lanedo com>
Date:   Tue Apr 1 16:29:19 2014 +0100

    extract: Incorrect inverse variable check for media_art_set()
    
    http://bugzilla.gnome.org/show_bug.cgi?id=727333

 libmediaart/extract.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/libmediaart/extract.c b/libmediaart/extract.c
index af409ee..dc0e79e 100644
--- a/libmediaart/extract.c
+++ b/libmediaart/extract.c
@@ -816,8 +816,8 @@ media_art_set (const unsigned char *buffer,
        gboolean retval = FALSE;
 
        g_return_val_if_fail (type > MEDIA_ART_NONE && type < MEDIA_ART_TYPE_COUNT, FALSE);
-       g_return_val_if_fail (artist == NULL, FALSE);
-       g_return_val_if_fail (title == NULL, FALSE);
+       g_return_val_if_fail (artist != NULL, FALSE);
+       g_return_val_if_fail (title != NULL, FALSE);
 
        /* What we do here:
         *