Server shutdown when PCM does not exist

[FAMILIAR-project]

Hi,

We have tried to load the following PCM https://opencompare.org/pcm/5757b9be975a3c01a5e5b477

the server is down.
We suspect it has problems to handle a non-existing PCM (with a non-existing ID)

Informations :
source: https://opencompare.org/

[FAMILIAR-project]

The trace

`/var/www/jsoc2/OpenCompare2/node_modules/mongodb/lib/utils.js:123
process.nextTick(function() { throw err; });
^

TypeError: Cannot read property '_id' of null
at new PCM (/var/www/jsoc2/OpenCompare2/public/js/pcm.js:11:13)
at /var/www/jsoc2/OpenCompare2/src/editSessionManager.js:33:20
at /var/www/jsoc2/OpenCompare2/src/db.js:59:13
at handleCallback (/var/www/jsoc2/OpenCompare2/node_modules/mongodb/lib/utils.js:120:56)
at /var/www/jsoc2/OpenCompare2/node_modules/mongodb/lib/collection.js:1417:5
at handleCallback (/var/www/jsoc2/OpenCompare2/node_modules/mongodb/lib/utils.js:120:56)
at /var/www/jsoc2/OpenCompare2/node_modules/mongodb/lib/cursor.js:682:5
at handleCallback (/var/www/jsoc2/OpenCompare2/node_modules/mongodb-core/lib/cursor.js:171:5)
at setCursorNotified (/var/www/jsoc2/OpenCompare2/node_modules/mongodb-core/lib/cursor.js:515:3)
at /var/www/jsoc2/OpenCompare2/node_modules/mongodb-core/lib/cursor.js:590:16
`