Getting domains fails with "undefined method 'organization' for nil:NilClass"

[philippthun]

Issue

Requests to /v3/domains and /v3/organizations/:org_guid/domains fail when user has a space-scoped role and one of the spaces for this role is deleted in parallel to handling one of the above requests.

Context

Getting readable orgs for space-scoped roles involves multiple database queries (i.e. first getting the space guids and then getting the org guid for each space). The current implementation cannot handle the situation when Space.find returns nil. This results in the following error: undefined method 'organization' for nil:NilClass leading to an HTTP 500 returned by cloud controller.

Steps to Reproduce

It's hard to reproduce, as it happens on huge foundations when there are users with access to many spaces and spaces getting deleted quite frequently (e.g. during some integration tests). It is possible to simulate the error in a debugger though (i.e. halt execution and delete rows from the database).

Expected result

Spaces that are gone should just be ignored.

Possible Fix

Use the safe navigation operator as done for the other <Model>.find occurrences in permissions.rb.