### Godot version

5ee983188de97ae027f9b9c1443438063f708a7e

### System information

Windows 11

### Issue description

Godot editor will throw an error and fail to generate preview icons for terrain tiles which use a base image which is not RGBA8 format.
`core\io\image.cpp:2788 - Condition "format != p_src->format" is true.`

### Steps to reproduce

- Import a non-RGBA8 image into Godot.
- Create a TileMap
- Create an associated TileSet
- Create a terrain for this tileset
- Add the image as an atlas
- Go to the paint tab
- Paint the terrain on the TileSet
- An error will occur any time terrains are edited in the TileSet editor or selected in the TileMap editor terrain tab.

### Minimal reproduction project

[tileset_terrain_bug.zip](https://github.com/godotengine/godot/files/13264213/tileset_terrain_bug.zip)

return false;
	} else if (components.size() == 1 && components[0].begins_with("pattern_") && components[0].trim_prefix("pattern_").is_valid_int()) {
		int pattern_index = components[0].trim_prefix("pattern_").to_int();
		if (pattern_index < 0 || pattern_index >= (int)patterns.size()) {
			return false;
		}
		r_ret = patterns[pattern_index];
		return true;
	}
	return false;
}
void TileSet::_get_property_list(List<PropertyInfo> *p_list) const {
	PropertyInfo property_info;
	
	p_list->push_back(PropertyInfo(Variant::NIL, GNAME("Rendering", ""), PROPERTY_HINT_NONE, "", PROPERTY_USAGE_GROUP));
	for (int i = 0; i < occlusion_layers.size(); i++) {
		p_list->push_back(PropertyInfo(Variant::INT, vformat("occlusion_layer_%d/light_mask", i), PROPERTY_HINT_LAYERS_2D_RENDER));
		
		property_info = PropertyInfo(Variant::BOOL, vformat("occlusion_layer_%d/sdf_collision", i));
		if (occlusion_layers[i].sdf_collision == false) {
			property_info.usage ^= PROPERTY_USAGE_STORAGE;
		}
		p_list->push_back(property_info);
	}
	
	p_list->push_back(PropertyInfo(Variant::NIL, GNAME("Physics", ""), PROPERTY_HINT_NONE, "", PROPERTY_USAGE_GROUP));
	for (int i = 0; i < physics_layers.size(); i++) {
		p_list->push_back(PropertyInfo(Variant::INT, vformat("physics_layer_%d/collision_layer", i), PROPERTY_HINT_LAYERS_2D_PHYSICS));
		
		property_info = PropertyInfo(Variant::INT, vformat("physics_layer_%d/collision_mask", i), PROPERTY_HINT_LAYERS_2D_PHYSICS);