Crashing after upgrade to newest node 12.6

[ignasg]

So I did node upgrade from 10.x and upgraded all packages, then started getting this error when saving a simple document on aws server.

{ aerospace: 'on', [__proto__]: {} }
error: [C:\Web\OldWeb\server.js] 2015-07-16 14:20 reference: 2f1faa1c0a ip: ::ff
ff:94.13.146.206
TypeError: Cannot read property 'ref' of undefined
    at model.Document.set (C:\Web\OldWeb\node_modules\mongoose\lib\document.js:4
49:74)
    at model.Document (C:\Web\OldWeb\node_modules\mongoose\lib\document.js:60:10
)
    at model.Model (C:\Web\OldWeb\node_modules\mongoose\lib\model.js:43:12)
    at new model (C:\Web\OldWeb\node_modules\mongoose\lib\model.js:2491:11)
    at C:\Web\OldWeb\structure\routes\resources\profile.js:502:64
    at C:\Web\OldWeb\node_modules\async\lib\async.js:251:17
    at C:\Web\OldWeb\node_modules\async\lib\async.js:154:25
    at C:\Web\OldWeb\node_modules\async\lib\async.js:248:21
    at C:\Web\OldWeb\node_modules\async\lib\async.js:612:34
    at async.series.user (C:\Web\OldWeb\structure\routes\resources\profile.js:32
4:21)

on this line:

&& !(this.schema.paths[key] && this.schema.paths[key].options.ref)

changing the last bit to something like:

this.schema.paths[key].options?this.schema.paths[key].options.ref:false)

seems to sort it out. Would you like a PR?