fix: approvals stuck on checking for conflicts

[ewingjm]

Purpose

Approving a solution merge would sometimes get stuck on the 'checking for conflicts' notification. This would happen if another development solution contained an entity which the development solution being approved did not contain.

Approach

Fixes an issue in the web resource where it was attempting to get subcomponents for an entity that wasn't in the solution.

TODOs

• [x] Automated test coverage for new code
• [x] Documentation updated (if required)
• [x] Build and tests successful