Error 500 is shown on changing id of a branch in branch page URL

Steps to reproduce:
1. Open some branch page (http://uat.jtalks.org/jcommune/branches/8, for example)
2. Change number in the URL to value '0' or '-1' (in URL: http://uat.jtalks.org/jcommune/branches/8 change value '8' to '0' or '-1')

Actual result: Error 500

Expected result: Error 404