Add try catch around method to guess system encoding.

[spdr870]

It crashes when trying to detect git.exe, causing this code to fail.

I got a new laptop. I wanted to install gitextensions, and I failed because of this. Needed to debug to fix this. This is not acceptable for new users.

Changes proposed in this pull request:

• Do not crash during auto-resolve git command. Not the best solution, but did not want to refactor gitmodule close before the release.

What did I do to test the code and ensure quality:

• Manual testing

Has been tested on (remove any that don't apply):

• Git Extensions 3.00.rc2
• Build 7931098 (Dirty)
• Git 2.19.2.windows.1
• Microsoft Windows NT 10.0.17134.0
• .NET Framework 4.7.3221.0
• DPI 120dpi (125% scaling)

[codecov]

Codecov Report

Merging #5820 into master will increase coverage by 0.35%.
The diff coverage is 50%.

@@            Coverage Diff            @@
##           master   #5820      +/-   ##
=========================================
+ Coverage   36.95%   37.3%   +0.35%     
=========================================
  Files         620     618       -2     
  Lines       47418   47385      -33     
  Branches     6322    6299      -23     
=========================================
+ Hits        17523   17677     +154     
+ Misses      29113   28933     -180     
+ Partials      782     775       -7

[drewnoakes]

Should this be targetted to the 3.0 branch?

[spdr870]

Should this be targetted to the 3.0 branch?

Yes, rebased on 3.0, thanks!