### Godot version

v4.0.beta.custom_build [fab9926a9]

### System information

Fedora 37

### Issue description

When creating a new inherited scene, saving the scene (for example with Ctrl+S) defaults to overwriting the scene being inherited, instead of prompting for a location to save to.

### Steps to reproduce

1. Create a new inherited scene
2. Press Ctrl+S

If the scene being inherited is imported (for example from a glTF), an error displays. If the inherited scene is a .tscn or .scn, it gets overridden by an inherited scene that tries to inherit itself, which is impossible and thus corrupt.

### Minimal reproduction project

N/A
Node *valid_source_owner = nullptr;
			if (source_node) {
				valid_source_owner = source_node->get_owner();
				while (valid_source_owner) {
					if (valid_source_owner == p_root) {
						break;
					}
					valid_source_owner = valid_source_owner->get_owner();
				}
			}
			if (!source_node || valid_source_owner == nullptr) {
				
				if (!c.callable.is_custom()) {
					valid_connections_from.push_back(c);
				}
			}
		}
		
		List<Node::GroupInfo> groups;
		p_node->get_groups(&groups);
		if (!modified_properties.is_empty() || !valid_connections_to.is_empty() || !valid_connections_from.is_empty() || !groups.is_empty()) {
			ModificationNodeEntry modification_node_entry;
			modification_node_entry.property_table = modified_properties;
			modification_node_entry.connections_to = valid_connections_to;
			modification_node_entry.connections_from = valid_connections_from;
			modification_node_entry.groups = groups;
			p_modification_table[p_root->get_path_to(p_node)] = modification_node_entry;
		}
	} else {
		AdditiveNodeEntry new_additive_node_entry;