[brasero] Fix a crash when there is no medium inserted

[Philippe Rouquier <philippr src gnome org>]

commit 9f83b226cd5782395b910c2592908b5f242bc20f
Author: Philippe Rouquier <bonfire-app wanadoo fr>
Date:   Wed May 27 20:06:24 2009 +0200

    Fix a crash when there is no medium inserted
---
 libbrasero-burn/brasero-track-disc.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/libbrasero-burn/brasero-track-disc.c b/libbrasero-burn/brasero-track-disc.c
index f92ff13..108b62c 100644
--- a/libbrasero-burn/brasero-track-disc.c
+++ b/libbrasero-burn/brasero-track-disc.c
@@ -181,13 +181,16 @@ brasero_track_disc_get_size (BraseroTrack *track,
 
 	priv = BRASERO_TRACK_DISC_PRIVATE (track);
 	medium = brasero_drive_get_medium (priv->drive);
+	if (!medium)
+		return BRASERO_BURN_NOT_READY;
+
 	brasero_medium_get_data_size (medium, &medium_size, &medium_blocks);
 
 	if (blocks)
 		*blocks = medium_blocks;
 
 	if (block_size)
-		*block_size = medium_size / medium_blocks;
+		*block_size = medium_blocks? (medium_size / medium_blocks):0;
 
 	return BRASERO_BURN_OK;
 }