"Error Signal" appears on pull requests when influxdb is not configured

# Bug report

A failed pull request occasionally get's an `Error Signal` context voted back in the pull request. The following is a screenshot example,

When the pull request is updated and fixed the `Error Signal` does not go away because there's no valid stage which votes back "success" for this status. It is confusing to end users who are using GitHub for pull requests and Jenkins for verifying pull requests.

# Desired behavior

`Error Signal` does not get reported to GitHub pull requests.

# Related closed issues

Since this is a new issue on a newer version I decided to open a new GitHub issue. This was earlier reported and fixed in #31 (Subject: Jenkins reports "Error signal" context on failure)

# Additional Information

Using:

* github-autostatus-plugin 3.5.0