### 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)

Array p = p_value;
				Vector2 last_coord;
				while (p.size() > 0) {
					if (p[0].get_type() == Variant::VECTOR2) {
						last_coord = p[0];
					} else if (p[0].get_type() == Variant::OBJECT) {
						ctd->autotile_occluder_map.insert(last_coord, p[0]);
					}
					p.pop_front();
				}
			} else if (what == "navpoly_map") {
				Array p = p_value;
				Vector2 last_coord;
				while (p.size() > 0) {
					if (p[0].get_type() == Variant::VECTOR2) {
						last_coord = p[0];
					} else if (p[0].get_type() == Variant::OBJECT) {
						ctd->autotile_navpoly_map.insert(last_coord, p[0]);
					}
					p.pop_front();
				}
			} else if (what == "priority_map") {
				Array p = p_value;
				Vector3 val;
				Vector2 v;
				int priority;
				while (p.size() > 0) {
					val = p[0];
					if (val.z > 1) {
						v.x = val.x;