Fix timeline Issues XSS Vulnerability

This patch fixes a XSS vulnerability that was assigned CVE-2013-1760 (related to Issue #1897). Although a fix was proposed for the latest release version, I found that the issue still exists. When a user creates a new bug report that contains JavaScript in the description of the report, the code will be executed if anyone visits the project Timeline (stored XSS). For reference: www.thebuggenie.com/security/TBGSN-002-1