[Critical Bug] Cannot save changes in an ink file in a subfolder properly due to an overwriting problem

**Critical bug:**
Add Folder/Folder/File.ink

Edit a line in File.ink.
The beginning of the edited line is overwritten by a copy of the last line in the file when saving it.
The lines between the edited line and the last line are inserted before the edited line.
(This might be a slightly imprecise description of the issue, but that is at least what I experience. At least some new text is overwritten by a copy of the last line in the file.)

**Not a critical bug, but annoying, and seems to be somehow connected to the first one:**
Add Folder/Folder/Folder/File.ink

File.ink always appear under unused files in addition to in the folder, although the INCLUDE directive is used correctly.

I have figured out that that these two issues arise in the following commit:
```
Commit: c06356de3913541c96e84d8c8194407633bae4ca [c06356d]
Parents: 5d7b710127
Author: Joseph Humfrey
Date: måndag 22. februar 2021 15:49:58
Committer: Joseph Humfrey
Fix for empty files causing saving issues
```

I made the code from master branch work properly again with these two bugs fixed, by making a new branch locally on my computer at:

```
Commit: 9e6d4930cea420e4cd54bf34b789c3aa2cb561bd [9e6d493]
Parents: 5d7b710127, a90fda4d2b
Author: Joseph Humfrey
Date: søndag 21. februar 2021 10:38:04
Committer: GitHub
Merge pull request #283 from Liance/keyboard-shortcuts

Keyboard shortcuts
```

and cherry-pick following commit:
```
Commit: 338262ee56f69191f96acd42ff24ca4e05b5aadd [338262e]
Parents: 436e28bb95, d730a947dd
Author: Joseph Humfrey
Date: tysdag 2. mars 2021 17:48:19
Committer: GitHub
Merge pull request #322 from fantabulous-tech/fix/highlighting-issues

Fix/highlighting issues
```