### Godot version

4.1.dev

### System information

Win11

### Issue description

I load a non-existing GDScript, but it still returns a valid instance instead of null.
```gdscript
@tool
extends EditorScript

func _run():
	var s = ResourceLoader.load("non_exists.gd", "", ResourceLoader.CACHE_MODE_IGNORE)
	print(s)
	assert(s == null)

```

```
  Attempt to open script 'res://non_exists.gd' resulted in error 'File not found'.
<GDScript#-9223369015982753437>
  res://new_script.gd:7 - Assertion failed.

```

### Steps to reproduce

N/A

### Minimal reproduction project

N/A
if (singleton == nullptr) {
		return;
	}
	MutexLock lock(singleton->mutex);
	if (singleton->cleared) {
		return;
	}
	for (KeyValue<String, HashSet<String>> &E : singleton->packed_scene_dependencies) {
		if (E.value.size() > 0 || !ResourceLoader::is_imported(E.key)) {
			continue;
		}
		singleton->packed_scene_dependencies.erase(E.key);
		singleton->packed_scene_cache.erase(E.key);
	}
}
void GDScriptCache::clear() {