Special characters are escaped repeatedly

[gera2ld]

Describe the bug Special characters are escaped repeatedly when editing an upload.

To Reproduce Steps to reproduce the behavior:

1. Go to https://pub.microbin.eu/
2. Create an upload with content Here is a symbol: $.
3. Click Edit and Save, the content becomes Here is a symbol: \$.
4. Click Edit again, the content becomes Here is a symbol: \\\$.

Expected behavior No redundant escaping.