(Slack) improvement: suppress possible irrelevant error on upgrade

[wolffberg]

Description

Non-terminating error is thrown when running choco upgrade slack -y

Fixes #65

Motivation and Context

Installer should run without errors even if slack.exe is not running.

How Has this Been Tested?

Command has been run in PowerShell V2.0 without errors both with and without slack.exe running.

Screenshot (if appropriate, usually isn't needed):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Migrated package (a package has been migrated from another repository)

Checklist:

• My code follows the code style of this repository.
• My change requires a change to documentation (this usually means the notes in the description of a package).
• I have updated the documentation accordingly (this usually means the notes in the description of a package).
• All files are up to date with the latest Contributing Guidelines
• The added/modified package passed install/uninstall in the chocolatey test environment.
• The changes only affect a single package (not including meta package).

[AppVeyorBot]

✅ Package verification completed without issues. PR is now pending human review

[hixio-mh]

Merged pull request

[mkevenaar]

LGTM!

[mkevenaar]

@wolffberg Your changes have been merged, this will ship with the next version of Slack and will come into play the version after that.

The chocolateyBeforeModify script gets called from the currently installed package version, not from the version pushed with this package.

Thank you for your contribution!