Check correct variable for null

[dennisvanderweide]

Description (*)

The wrong variable is being checked for null, which can cause a null reference exception in the bulk source transfer

Contribution checklist (*)

• [x] Pull request has a meaningful description of its purpose
• [x] All commits are accompanied by meaningful commit messages
• [x] All new or changed code is covered with unit/integration tests (if applicable)
• [x] All automated tests passed successfully (all builds are green)