[openbox] fix xdg-menu to not crash without icon file (#737112)

[Miroslav Lichvar]

commit 32214976a02be8297ae8d8f40f3aef4b53d17820
Author: Ralph Giles <giles at xiph.org>
Date:   Mon Oct 10 14:52:52 2011 +0200

    fix xdg-menu to not crash without icon file (#737112)

 xdg-menu |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/xdg-menu b/xdg-menu
index 71f9026..4f16438 100644
--- a/xdg-menu
+++ b/xdg-menu
@@ -48,7 +48,8 @@ def icon_attr(entry):
 	if iconinfo:
 		iconfile = iconinfo.get_filename()
 		iconinfo.free()
-		return ' icon="' + iconfile + '"'
+		if iconfile:
+			return ' icon="' + iconfile + '"'
 	return ''
 
 def entry_name(entry):