Gracefully handle OhDear SDK errors

This is gone after we don't do error-logging/throwing in service constructors anymore, i.e. with 📌 Dependency injection anti-patterns Needs review applied:

$ drush ohdear:info

In OhDearSdkService.php line 89:

  OhDear API key is missing.

Just setting this to Needs Review because I can't really close it myself yet until after you approve #3403202.

There is also an issue when visiting /admin/reports/ohdear/info. The site breaks if api key is wrong or missing. Controller probably needs some error handling or the ohdear service.