LADX: Moved ROM requirement from generate_output to stage_assert_gene…

…rate. (ArchipelagoMW#3540)

Co-authored-by: Mrks <markus.burmeister@mburm.de>

worlds/ladx/__init__.py

@@ -7,7 +7,7 @@
 import bsdiff4
 
 import settings
-from BaseClasses import Entrance, Item, ItemClassification, Location, Tutorial
+from BaseClasses import Entrance, Item, ItemClassification, Location, Tutorial, MultiWorld
 from Fill import fill_restrictive
 from worlds.AutoWorld import WebWorld, World
 from .Common import *
@@ -24,7 +24,7 @@
 from .Locations import (LinksAwakeningLocation, LinksAwakeningRegion,
                         create_regions_from_ladxr, get_locations_to_id)
 from .Options import DungeonItemShuffle, links_awakening_options, ShuffleInstruments
-from .Rom import LADXDeltaPatch
+from .Rom import LADXDeltaPatch, get_base_rom_path
 
 DEVELOPER_MODE = False
 
@@ -433,6 +433,12 @@ def guess_icon_for_other_world(self, other):
 
         return "TRADING_ITEM_LETTER"
 
+    @classmethod
+    def stage_assert_generate(cls, multiworld: MultiWorld):
+        rom_file = get_base_rom_path()
+        if not os.path.exists(rom_file):
+            raise FileNotFoundError(rom_file)
+
     def generate_output(self, output_directory: str):
         # copy items back to locations
         for r in self.multiworld.get_regions(self.player):