App pre-migration checks running after removing all apps from migration

Issue Summary

This is reproducible on Data Center: yes

Steps to Reproduce

1. Create a migration plan including only a Stage 1 app marked as 'needed in cloud'
2. Run preflight checks
3. Remove app using the 'Remove 1 app from this migration' button from failed reliability check

Expected Results

No app checks are triggered if all apps are removed

Actual Results

All app checks re-run showing successful results

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available