[gnome-epub-thumbnailer] main: Bail if we couldn't load any cover data

[Bastien Nocera <hadess src gnome org>]

commit f12d7bda0abba98f2c5cbd86bab0ed8daac7a814
Author: Bastien Nocera <hadess hadess net>
Date:   Sat Jul 13 14:26:08 2013 +0200

    main: Bail if we couldn't load any cover data
    
    Rather than barf later on.

 gnome-epub-thumbnailer.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)
---
diff --git a/gnome-epub-thumbnailer.c b/gnome-epub-thumbnailer.c
index a482ecd..21f7ae3 100644
--- a/gnome-epub-thumbnailer.c
+++ b/gnome-epub-thumbnailer.c
@@ -321,6 +321,11 @@ int main (int argc, char **argv)
 
        g_free (input_filename);
 
+       if (cover_data == NULL) {
+               g_warning ("Could not find cover file in '%s'", filenames[0]);
+               return 1;
+       }
+
        mem_stream = g_memory_input_stream_new_from_data (cover_data, length, g_free);
        pixbuf = gdk_pixbuf_new_from_stream_at_scale (mem_stream, output_size, -1, TRUE, NULL, NULL);
        g_object_unref (mem_stream);