CustomServer: properly 'inherit' Archipelago from static_server_data (#…

…3366)

This fixes a potential exception during room spin-up.

WebHostLib/customserver.py

@@ -106,9 +106,9 @@ def load(self, room_id: int):
         static_gamespackage = self.gamespackage  # this is shared across all rooms
         static_item_name_groups = self.item_name_groups
         static_location_name_groups = self.location_name_groups
-        self.gamespackage = {"Archipelago": static_gamespackage["Archipelago"]}  # this may be modified by _load
-        self.item_name_groups = {}
-        self.location_name_groups = {}
+        self.gamespackage = {"Archipelago": static_gamespackage.get("Archipelago", {})}  # this may be modified by _load
+        self.item_name_groups = {"Archipelago": static_item_name_groups.get("Archipelago", {})}
+        self.location_name_groups = {"Archipelago": static_location_name_groups.get("Archipelago", {})}
 
         for game in list(multidata.get("datapackage", {})):
             game_data = multidata["datapackage"][game]