TypeError: Cannot read property 'length' of undefined
   at Docset._loadCourseIndex (/home/doc/cw-app/lib/Docset.js:51:20)
   at new Docset (/home/doc/cw-app/lib/Docset.js:14:20)
   at /home/doc/cw-app/lib/doc-route.js:63:18
   at Layer.handle [as handle_request] (/home/doc/cw-app/node_modules/express/lib/router/layer.js:82:5)
   at next (/home/doc/cw-app/node_modules/express/lib/router/route.js:100:13)
   at Route.dispatch (/home/doc/cw-app/node_modules/express/lib/router/route.js:81:3)
   at Layer.handle [as handle_request] (/home/doc/cw-app/node_modules/express/lib/router/layer.js:82:5)
   at /home/doc/cw-app/node_modules/express/lib/router/index.js:234:24
   at param (/home/doc/cw-app/node_modules/express/lib/router/index.js:331:14)
   at param (/home/doc/cw-app/node_modules/express/lib/router/index.js:347:14)
   at param (/home/doc/cw-app/node_modules/express/lib/router/index.js:347:14)
   at param (/home/doc/cw-app/node_modules/express/lib/router/index.js:347:14)
   at param (/home/doc/cw-app/node_modules/express/lib/router/index.js:347:14)
   at Function.proto.process_params (/home/doc/cw-app/node_modules/express/lib/router/index.js:391:3)
   at /home/doc/cw-app/node_modules/express/lib/router/index.js:228:12
   at Function.match_layer (/home/doc/cw-app/node_modules/express/lib/router/index.js:295:3)