### 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)

add_occlusion_layer();
				}
				set_occlusion_layer_light_mask(index, p_value);
				return true;
			} else if (components[1] == "sdf_collision") {
				ERR_FAIL_COND_V(p_value.get_type() != Variant::BOOL, false);
				while (index >= occlusion_layers.size()) {
					add_occlusion_layer();
				}
				set_occlusion_layer_sdf_collision(index, p_value);
				return true;
			}
		} else if (components.size() == 2 && components[0].begins_with("physics_layer_") && components[0].trim_prefix("physics_layer_").is_valid_int()) {
			
			int index = components[0].trim_prefix("physics_layer_").to_int();
			ERR_FAIL_COND_V(index < 0, false);
			if (components[1] == "collision_layer") {
				ERR_FAIL_COND_V(p_value.get_type() != Variant::INT, false);
				while (index >= physics_layers.size()) {
					add_physics_layer();
				}
				set_physics_layer_collision_layer(index, p_value);
				return true;
			} else if (components[1] == "collision_mask") {
				ERR_FAIL_COND_V(p_value.get_type() != Variant::INT, false);
				while (index >= physics_layers.size()) {
					add_physics_layer();
				}
				set_physics_layer_collision_mask(index, p_value);
				return true;