Fix parsing shortId

It is also possible to have letters as shortId.
2 jobs for 537-question-wall-is-not-displayed-if-the-room-id-is-a-string in 10 minutes and 19 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Codestyle
passed #247311
nodejs
tslint

00:02:28

 
  Build
passed #247312
angular
ngbuild

00:07:50