Remove unloaded objects from nested relationshps

[veelenga]

Explanation of the issue

Let's say we have nested objects to save:

event: [shows: [tickets]]

and we create a new ticket (which belongs to the show).

In that case, the reset relationships function doesn't remove the created in the store record from the list of tickets.

Before save:

show.tickets.mapBy('id') // => [1,2]

after save:

show.tickets.mapBy('id') // => [1,2,3, null]

The explanation of the fix

Now, we properly remove the null object from the relationships and unload it.

Basically, we just had to remove that from the correct parent. Before, the extension was trying to remove ticket from top-level object (i.e. event)

[pavloo]

makes sense