Merge pull request #510 from jfolkins/fix_sessregenid

fix: added nil check on c.CruSession to prevent crash

@@ -397,7 +397,9 @@ func (c *Controller) DelSession(name interface{}) {
 // SessionRegenerateID regenerates session id for this session.
 // the session data have no changes.
 func (c *Controller) SessionRegenerateID() {
+	if c.CruSession != nil {
 		c.CruSession.SessionRelease(c.Ctx.ResponseWriter)
+	}
 	c.CruSession = GlobalSessions.SessionRegenerateId(c.Ctx.ResponseWriter, c.Ctx.Request)
 	c.Ctx.Input.CruSession = c.CruSession
 }