### 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)

tile_property_list.push_back(property_info);
		
		property_info = PropertyInfo(Variant::INT, "animation_columns", PROPERTY_HINT_NONE, "", PROPERTY_USAGE_NO_EDITOR);
		if (E_tile.value.animation_columns == 0) {
			property_info.usage ^= PROPERTY_USAGE_STORAGE;
		}
		tile_property_list.push_back(property_info);
		
		property_info = PropertyInfo(Variant::INT, "animation_separation", PROPERTY_HINT_NONE, "", PROPERTY_USAGE_NO_EDITOR);
		if (E_tile.value.animation_separation == Vector2i()) {
			property_info.usage ^= PROPERTY_USAGE_STORAGE;
		}
		tile_property_list.push_back(property_info);
		
		property_info = PropertyInfo(Variant::FLOAT, "animation_speed", PROPERTY_HINT_NONE, "", PROPERTY_USAGE_NO_EDITOR);
		if (E_tile.value.animation_speed == 1.0) {
			property_info.usage ^= PROPERTY_USAGE_STORAGE;
		}
		tile_property_list.push_back(property_info);
		
		property_info = PropertyInfo(Variant::INT, "animation_mode", PROPERTY_HINT_NONE, "", PROPERTY_USAGE_NO_EDITOR);
		if (E_tile.value.animation_mode == TILE_ANIMATION_MODE_DEFAULT) {
			property_info.usage ^= PROPERTY_USAGE_STORAGE;
		}
		tile_property_list.push_back(property_info);
		
		tile_property_list.push_back(PropertyInfo(Variant::INT, "animation_frames_count", PROPERTY_HINT_NONE, "", PROPERTY_USAGE_NONE));
		
		bool store_durations = tiles[E_tile.key].animation_frames_durations.size() >= 2;
		for (int i = 0; i < (int)tiles[E_tile.key].animation_frames_durations.size(); i++) {