fix crash on play/start with empty world list

make enter button work in create world dialog

builtin/mainmenu.lua

@@ -332,6 +332,10 @@ function menu.filtered_index_to_plain(filtered_index)
 	
 	local temp_idx = 0
 	
+	if menu.worldlist == nil then
+		return -1
+	end
+	
 	for i=1,#menu.worldlist,1 do
 		if menu.worldlist[i].gameid == current_game.id then
 			temp_idx = temp_idx +1
@@ -418,6 +422,10 @@ function menu.update_last_game(world_idx)
 	if gamedata.selected_world <= #menu.worldlist then
 		local world = menu.worldlist[gamedata.selected_world]
 		
+		if world == nil then
+			return
+		end
+		
 		for i=1,#gamemgr.games,1 do		
 			if gamemgr.games[i].id == world.gameid then
 				menu.last_game = i
@@ -574,7 +582,8 @@ end
 --------------------------------------------------------------------------------
 function tabbuilder.handle_create_world_buttons(fields)
 	
-	if fields["world_create_confirm"] then
+	if fields["world_create_confirm"] or
+		fields["key_enter"] then
 		
 		local worldname = fields["te_world_name"]
 		local gameindex = engine.get_textlist_index("games")

src/main.cpp

@@ -1667,7 +1667,8 @@ int main(int argc, char *argv[])
 				}
 				
 				// Set world path to selected one
-				if(menudata.selected_world != -1){
+				if ((menudata.selected_world >= 0) &&
+					(menudata.selected_world < worldspecs.size())) {
 					worldspec = worldspecs[menudata.selected_world];
 					infostream<<"Selected world: "<<worldspec.name
 							<<" ["<<worldspec.path<<"]"<<std::endl;