Fix crashes with mobs below or above due division by zero

* removes a division by zero issue which returns nan for yaw
  in some places

mods/affects/chatcommands.lua

@@ -5,7 +5,9 @@ minetest.register_chatcommand("affect",{
 	privs = {affects=true},
 	func = function (name, param)
 		local aname, affectid = string.match(param, "([^ ]+) (.+)")	
-		if ( affects.affectPlayer(aname,affectid) ) then
+		if ( aname == nil or aname == "" or affectid == nil or affectid == '' ) then
+			minetest.chat_send_player(name, "Syntax: affect <name> <affectid>")
+		elseif ( affects.affectPlayer(aname,affectid) ) then
 			minetest.chat_send_player(name,aname.." has been affected by "..affects._affects[affectid].name)
 		else
 			minetest.chat_send_player(name,"Unable to affect "..aname.." with "..affectid)

mods/mobs/api.lua

@@ -638,7 +638,14 @@ end
 function mobs:face_pos(self,pos)
 	local s = self.object:getpos()
 	local vec = {x=pos.x-s.x, y=pos.y-s.y, z=pos.z-s.z}
-	local yaw = math.atan(vec.z/vec.x)+math.pi/2
+	local yaw = 0
+	if vec.x ~= 0 then
+		yaw=math.atan(vec.z/vec.x)+math.pi/2
+	else
+		if vec.z>0 then
+			yaw=math.pi
+		end
+	end
 	if self.drawtype == "side" then
 		yaw = yaw+(math.pi/2)
 	end

mods/mobs/step.lua

@@ -144,7 +144,14 @@ function mobs.on_step(self,dtime)
 		end
 		
 		local vec = {x=p.x-s.x, y=p.y-s.y, z=p.z-s.z}
-		local yaw = math.atan(vec.z/vec.x)+math.pi/2
+		local yaw = 0
+		if vec.x ~= 0 then
+			yaw=math.atan(vec.z/vec.x)+math.pi/2
+		else
+			if vec.z>0 then
+				yaw=math.pi
+			end
+		end
 		if self.drawtype == "side" then
 			yaw = yaw+(math.pi/2)
 		end
@@ -223,7 +230,13 @@ function mobs.on_step(self,dtime)
 		end
 		
 		local vec = {x=p.x-s.x, y=p.y-s.y, z=p.z-s.z}
-		local yaw = math.atan(vec.z/vec.x)+math.pi/2
+		if vec.x ~= 0 then
+			yaw=math.atan(vec.z/vec.x)+math.pi/2
+		else
+			if vec.z>0 then
+				yaw=math.pi
+			end
+		end
 		if self.drawtype == "side" then
 			yaw = yaw+(math.pi/2)
 		end
@@ -345,7 +358,13 @@ function mobs.on_step(self,dtime)
 				self.v_start = false
 			else
 				local vec = {x=p.x-s.x, y=p.y-s.y, z=p.z-s.z}
-				local yaw = math.atan(vec.z/vec.x)+math.pi/2
+				if vec.x ~= 0 then
+					yaw=math.atan(vec.z/vec.x)+math.pi/2
+				else
+					if vec.z>0 then
+						yaw=math.pi
+					end
+				end
 				if self.drawtype == "side" then
 					yaw = yaw+(math.pi/2)
 				end

mods/quests/chest.lua

@@ -3,8 +3,12 @@ quests.chest = {}
 quests.chest.go = function(npc,player)
   local inv = player:get_inventory()
   local pos = npc.object:getpos()
-  if inv:contains_item("main","farming_plus:flour") and inv:contains_item("main","food:bowl") then
-    inv:remove_item("main","farming_plus:flour")
+  if (inv:contains_item("main","farming_plus:flour") or inv:contains_item("main","food:flour")) and inv:contains_item("main","food:bowl") then
+    if inv:contains_item("main","farming_plus:flour") then 
+      inv:remove_item("main","farming_plus:flour")
+    else  
+      inv:remove_item("main","food:flour")
+    end
     inv:remove_item("main","food:bowl")
     chat.local_chat(pos,"'Thank you very much, take this as a token of my appreciation!'",6)
     local lp = player:getpos()