express 4 jade invalid error

I am using express 4 with jade. I have an error in the jade template like this:

file: test.jade, data.item.test is undefined:

extends layout

block content
if data.item.test
    div.content-section

the html response looks like this:

TypeError: /work/web/views/layout.jade:37
   35|                 header
   36|                   i.arrow-up
 > 37|                   h4.user-name #{user.firstName.charAt(0).toUpperCase() + user.firstName.slice(1)} #{user.lastName.charAt(0).toUpperCase() + user.lastName.slice(1)}
   38|                   a(href="/profile").edit-profile
   39|                     i
   40|                     | Edit Profile

Cannot read property 'firstName' of undefined

if I fix the actual error in the jade template, everything will work fine and no error will be reported in the layout.

How can I fix this because it's very difficult to debug errors in jade templates