### Godot version

4.01

### System information

Windows 10

### Issue description

It seems a tiles Custom Data is cleared/not set when "Local to Scene" is enabled for the TileMap in the Resource section. At least the custom data isn't set by the time of the _ready function in the script attached to the TileMap.

### Steps to reproduce

create TileMap and tileset with custom data and attached script. in _ready method attempt to read custom data from a used cell. 

In Attached project run it. It will print_debug if it found custom data or not. "Local to Scene" is enabled so it will not find the custom data.

### Minimal reproduction project

[TileMapCustomDataLocalBugReproduce.zip](https://github.com/godotengine/godot/files/11470771/TileMapCustomDataLocalBugReproduce.zip)

TERRAIN_MODE_MATCH_CORNERS_AND_SIDES = 0,
		TERRAIN_MODE_MATCH_CORNERS,
		TERRAIN_MODE_MATCH_SIDES,
	};
	enum TileShape {
		TILE_SHAPE_SQUARE,
		TILE_SHAPE_ISOMETRIC,
		TILE_SHAPE_HALF_OFFSET_SQUARE,
		TILE_SHAPE_HEXAGON,
	};
	enum TileLayout {
		TILE_LAYOUT_STACKED,
		TILE_LAYOUT_STACKED_OFFSET,
		TILE_LAYOUT_STAIRS_RIGHT,
		TILE_LAYOUT_STAIRS_DOWN,
		TILE_LAYOUT_DIAMOND_RIGHT,
		TILE_LAYOUT_DIAMOND_DOWN,
	};
	enum TileOffsetAxis {