Fix various quest issues

- Fix global variable 'quests' (quests/init.lua)
 - Fix minetest.register_on_dignode's function to handle the rare case where 'digger' == nil
   (mff/mff_quests/init.lua)
 - Made the only available quests (yet) more explicit (mff/mff_quests/init.lua)

mods/mff/mff_quests/init.lua

@@ -17,9 +17,9 @@ mff.QPREFIX = "mff_quests:"
 
 mff.quests.quests = {
 	testdiggydiggyhole = {
-		title = "Dig 10 nodes",
+		title = "Dig 10 stone nodes",
 		max = 10,
-		desc = "As long as you can not dig, you are not a real miner.",
+		desc = "As long as you can not dig stone, you are not a real miner.",
 		periodicity = 10,
 		objective = {
 			dig = {"default:stone"}
@@ -84,6 +84,7 @@ end
 
 -- For quests where you have to dig something, the updates happen here
 minetest.register_on_dignode(function(pos, oldnode, digger)
+	if not digger then return end -- Already happened before
 	local qstatus = mff.quests.quest_status[digger:get_player_name()]
 	for qname, quest in pairs(mff.quests.quests) do
 		if qstatus[qname] ~= nil and qstatus[qname] >= 0 then
@@ -116,4 +117,4 @@ end)
 
 minetest.register_on_shutdown(function()
 	-- TODO save data
-end)
+end)

mods/quests/init.lua

@@ -1,5 +1,6 @@
 -- reading previous quests
 local file = io.open(minetest.get_worldpath().."/quests", "r")
+quests = {}
 if file then
 	minetest.log("action", "Reading quests...")
 	quests = minetest.deserialize(file:read("*all"))