Description of the Issue

Setting the Custom Backup Directory using an environment variable like "%TMP%..\backups" does not work any more - it did in V6.*
If I try to save a file I get the following warning dialog:

File Backup Failed

The previous version of the file could not be saved into the backup directory at "%TMP%..\backups\name.2016-11-03_120930.bak".

Do you want to save the current file anyways?

Yes No

Steps to Reproduce the Issue

1. Just set the Custom Backup Directory to %TMP%..\backups\
2. Make sure that the folder exists

Expected Behavior

Environment variables should be evaluated if given in the name of the Custom Backup Directory. (If the folder does not exist, it should be tried to create it?)

Actual Behavior

A warning dialog appears, see description

Debug Information

Notepad++ v7.2 (32-bit)
Build time : Nov 2 2016 - 11:26:20
Path : D:_\Tools\NotePad++\notepad++.exe
Admin mode : ON
Local Conf mode : ON
OS : Windows 7
Plugins : mimeTools.dll NppConverter.dll NppExec.dll NppExport.dll NppTextFX.dll PluginManager.dll SpellChecker.dll WindowManager.dll XMLTools.dll