UI: Fixed `nano` not correctly opening a script in root of a server if `cd`'d into a directory

[cptpiepmatz]

This PR fixes nano opening the incorrect file in the root directory if you cd'd into a directory.

Expected Behavior

The script editor should open the correct file when you click on a file name of the root directory while having a directory currently opened/displayed.

Steps to reproduce

1. Create a file in root directory.
2. Execute ls command.
3. Create a file in a directory.
4. Navigate to directory via cd.
5. Click on the file link of the previous ls.

Currently this opens a file in the current directory with the name of file in the root directory.

Checks made this works

I created multiple files in different and differently nested directories. I executed ls on all directories and opened all files from every selected directory. For me this seems to work now.

[quacksouls]

I'm no good at reading the code, but can at least confirm the buggy behaviour. Before applying the PR:

Bitburner v2.1.0 (8f4636cb)
[home ~/]> ls
dirB/ 
hackers-starting-handbook.lit 
NUKE.exe 
scriptA.js 
scriptB.js
[home ~/]> cd dirB/
[home ~/dirB]> ls
dirC/ 
scriptB.js 
[home ~/dirB]> cd dirC/
[home ~/dirB/dirC]> ls
scriptA.js 
scriptB.js
[home ~/dirB/dirC]>

1. Click on scriptA.js from /dirB/dirC/ opens the file /dirB/dirC/scriptA.js.
2. Click on scriptA.js from root / opens /dirB/dirC/scriptA.js, but the expected behaviour is to open the file /scriptA.js.
3. Click on scriptB.js from root / opens the file /dirB/dirC/scriptB.js, whereas the expected behaviour should be to open the file /scriptB.js. If the file /dirB/dirC/scriptB.js does not exist, then this action opens a non-existent file /dirB/dirC/scriptB.js.
4. Click on scriptB.js from /dirB and it correctly opens the file /dirB/scriptB.js.

After applying the PR, the above test cases would open the expected file from the correct directory.