### 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
parameters_names.write[j] = member.signal->parameters[j]->identifier->name;
						}
						_signals[member.signal->identifier->name] = parameters_names;
					} break;
					case GDScriptParser::ClassNode::Member::GROUP: {
						members_cache.push_back(member.annotation->export_info);
					} break;
					default:
						break; 
				}
			}
		} else {
			placeholder_fallback_enabled = true;
			return false;
		}
	} else if (placeholder_fallback_enabled) {
		return false;
	}
	placeholder_fallback_enabled = false;
	if (base_cache.is_valid() && base_cache->is_valid()) {
		for (int i = 0; i < base_caches.size(); i++) {
			if (base_caches[i] == base_cache.ptr()) {
				if (r_err) {
					*r_err = true;
				}
				valid = false; 
				base_cache->valid = false;
				base_cache->inheriters_cache.clear(); 
				base_cache.unref();
				base.unref();