From 848998003939d1617dad649dc9842b11ffc83ead Mon Sep 17 00:00:00 2001
From: sapier <Sapier at GMX dot net>
Date: Sun, 25 Aug 2013 00:43:20 +0200
Subject: [PATCH] Add sanity check to sort function

---
 builtin/filterlist.lua | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/builtin/filterlist.lua b/builtin/filterlist.lua
index fd337ae9..1c2ceb03 100644
--- a/builtin/filterlist.lua
+++ b/builtin/filterlist.lua
@@ -240,6 +240,12 @@ end
 function sort_worlds_alphabetic(this) 
 
 	table.sort(this.m_processed_list, function(a, b)
+		--fixes issue #857 (crash due to sorting nil in worldlist)
+		if a == nil or b == nil then
+			if a == nil and b ~= nil then return false end
+			if b == nil and a ~= nil then return true end
+			return false
+		end
 		if a.name:lower() == b.name:lower() then
 			return a.name < b.name
 		end