Fix 'Error: Can't set headers after they are sent.'

[JacksonBates]

Error log:

2017-11-09T20:57:36.191329+00:00 app[web.1]: Error: Can't set headers after they are sent.
2017-11-09T20:57:36.191341+00:00 app[web.1]:     at validateHeader (_http_outgoing.js:504:11)
2017-11-09T20:57:36.191342+00:00 app[web.1]:     at ServerResponse.setHeader (_http_outgoing.js:511:3)
2017-11-09T20:57:36.191343+00:00 app[web.1]:     at ServerResponse.header (/app/node_modules/express/lib/response.js:767:10)
2017-11-09T20:57:36.191343+00:00 app[web.1]:     at ServerResponse.send (/app/node_modules/express/lib/response.js:170:12)
2017-11-09T20:57:36.191344+00:00 app[web.1]:     at done (/app/node_modules/express/lib/response.js:1004:10)
2017-11-09T20:57:36.191344+00:00 app[web.1]:     at tryHandleCache (/app/node_modules/ejs/lib/ejs.js:228:10)
2017-11-09T20:57:36.191345+00:00 app[web.1]:     at View.exports.renderFile [as engine] (/app/node_modules/ejs/lib/ejs.js:437:10)
2017-11-09T20:57:36.191346+00:00 app[web.1]:     at View.render (/app/node_modules/express/lib/view.js:135:8)
2017-11-09T20:57:36.191347+00:00 app[web.1]:     at tryRender (/app/node_modules/express/lib/application.js:640:10)
2017-11-09T20:57:36.191347+00:00 app[web.1]:     at Function.render (/app/node_modules/express/lib/application.js:592:3)