• Enter a server with an unknown RSA key fingerprint in "Tools" -> "Options..." -> "Version Control" -> "Gerrit".
• Open a Gerrit window using "Tools" -> "Git" -> "Gerrit...".
  The Gerrit window will stay empty. A progress bar will show up but neither move nor disappear.

In this case, Creator should at least display the error message which would be shown when running the query on the command line.