### Godot version

v4.1.rc2.official [46424488e]

### System information

Godot v4.1.rc2 - Linux Mint 20 (Ulyana) - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 2060 SUPER (nvidia; 515.105.01) - Intel(R) Core(TM) i7-6700K CPU @ 4.00GHz (8 Threads)

### Issue description

Dragging and dropping a file to a new position inside its current folder, or onto the icon for its current folder - when that folder is the project root folder :res// - will be treated as though you were dropping a different file with the same name.

Expectation: for nothing to happen.

Also tried it in 4.0.3 and 4.1-dev3, where it behaves as expected.

https://github.com/godotengine/godot/assets/64640811/90de1120-dd92-41b8-b202-db77c343103a

### Steps to reproduce

1. New or existing project.
2. Click and drag a file in :res// in FileSystem dock.
3. Drop the file back into :res//.
4. Be prompted to overwrite or rename.

### Minimal reproduction project

N/A
Ref<InputEventMouseMotion> mm = p_event;
	if (mm.is_valid() && holding_branch) {
		const int item_idx = files->get_item_at_position(mm->get_position());
		if (item_idx != -1) {
			files->deselect_all();
			String fpath = files->get_item_metadata(item_idx);
			if (fpath.ends_with("/") || fpath == "res://") {
				files->select(item_idx);
			}
			TreeItem *deselect_item = tree->get_next_selected(tree->get_root());
			while (deselect_item) {
				deselect_item->deselect(0);
				deselect_item = tree->get_next_selected(deselect_item);
			}
			
			TreeItem *tree_item = tree->get_item_with_text(files->get_item_text(item_idx));
			if (tree_item) {
				tree_item->select(0);
			} else {
				
				fpath = fpath.substr(0, fpath.rfind("/") + 1);
				if (fpath.size() > String("res://").size()) {
					fpath = fpath.left(fpath.size() - 2); 
					const int slash_idx = fpath.rfind("/");