[gthumb] Do not process bitmap thumbnails with invalid color settings.

[Paolo Bacchilega <paobac src gnome org>]

commit d9bc1ffa56695a1ffd278bfc7ea063987c844532
Author: Jan de Groot <jgc archlinux org>
Date:   Mon Feb 13 13:28:27 2017 +0000

    Do not process bitmap thumbnails with invalid color settings.
    
    Libraw sets these to 0 in an excption handler, we should not assert fatal when processing such an image.
    
    [bug #778556]

 extensions/raw_files/main.c |   16 ++++++++++------
 1 files changed, 10 insertions(+), 6 deletions(-)
---
diff --git a/extensions/raw_files/main.c b/extensions/raw_files/main.c
index 6cf2ff8..9c55e72 100644
--- a/extensions/raw_files/main.c
+++ b/extensions/raw_files/main.c
@@ -267,12 +267,16 @@ _cairo_image_surface_create_from_raw (GInputStream  *istream,
                                                        error);
                        break;
                case LIBRAW_THUMBNAIL_BITMAP:
-                       image = _libraw_read_bitmap_data (raw_data->thumbnail.twidth,
-                                                         raw_data->thumbnail.theight,
-                                                         raw_data->thumbnail.tcolors,
-                                                         8,
-                                                         (guchar *) raw_data->thumbnail.thumb,
-                                                         raw_data->thumbnail.tlength);
+                       if ((raw_data->thumbnail.tcolors > 0) && (raw_data->thumbnail.tcolors <= 4)) {
+                               image = _libraw_read_bitmap_data (raw_data->thumbnail.twidth,
+                                                                 raw_data->thumbnail.theight,
+                                                                 raw_data->thumbnail.tcolors,
+                                                                 8,
+                                                                 (guchar *) raw_data->thumbnail.thumb,
+                                                                 raw_data->thumbnail.tlength);
+                       }
+                       else
+                               g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_INVALID_DATA, "Unsupported 
data format");
                        break;
                default:
                        g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_INVALID_DATA, "Unsupported data 
format");