Bug: Tab separator randomly appears with only one tab open

### Description

When opening files, there is a random chance that a tab separator will be visible regardless of how many tabs were open before closing the app window.


### Steps To Reproduce

1. Open Files;
2. Close the app while leaving it running in the background;
3. Continously open and close the app until the separator appears.

### Requirements

The tab separator should only be visible when more than one tab is open

### Files Version

3.5.0.0

### Windows Version

Windows 11 Pro 23H2 22631.3880

### Log File

[debug.log](https://github.com/user-attachments/files/16329567/debug.log)