Allow HipChat API version to be blank and default to v2
What does this MR do?
This MR fixes a regression introduced in v7.11 that requires a HipChat API version to be specified when it is supposed to be optional.
Why was this MR needed?
The "optional" HipChat API version in 57c72455 passed in a blank api_version
when nothing was specified, and the code was not tested. This would cause a 500 Error.
What are the relevant issue numbers?
Closes #772 (closed)