Deleting a file shows a mode change to undefined

[Arcanemagus]

Prerequisites

• Have you tried to reproduce the problem in Safe Mode?
• Have you followed all applicable steps in the debugging guide?
• Have you checked the FAQs on the message board for common solutions?
• Have you checked that your issue isn't already filed?

Description

When a file with a non-standard file mode (such as 100755) is deleted the following is shown:

Although this message isn't technically wrong, it doesn't exactly sound right either.

Steps to Reproduce

1. Have a git repository with a file with a special mode specified on it.
2. Delete the file
3. Preview the file change

Expected behavior:

Since the file is being deleted entirely and this is shown by the deleted icon in the file list, as well as the entire contents being shown as removed, I think this entire file mode section should just not show.

For reference, files with the normal mode (100644) that are being deleted don't show this dialog.

Actual behavior:

A "file mode change" is shown saying it has been changed to undefined.

Reproduces how often:

100% of the time.

Versions

OS: Windows 10 x64 Enterprise
Github package: v0.12.0

Atom    : 1.26.0-beta1
Electron: 1.7.11
Chrome  : 58.0.3029.110
Node    : 7.9.0
apm  1.19.0
npm  3.10.10
node 6.9.5 x64
atom 1.26.0-beta1
python 2.7.14
git 2.17.0.windows.1
visual studio 2015

Additional Information

Handling of filemode changes was initially added in #1275.