Server: fix unbound exception variable

[dshemetov]

Small accident, quick fix. Likely gets caught somewhere else anyway, but better to be explicit.

Prerequisites:

• Unless it is a documentation hotfix it should be merged against the dev branch
• Branch is up-to-date with the branch to be merged with, i.e. dev
• Build is successful
• Code is cleaned up and formatted

Summary

An exception variable got unbound, even though it is used.

[melange396]

getting to this line doesnt seem likely to happen in production but leaving it as-is could be problematic and produce strange artifacts in logging and for the client, so im going to merge it back in for the next release.