Docgen fails to export Started on and Finished on dates for TestRuns

Description
Docgen fails to export Started on and Finished on dates for TestRuns

How to reproduce

1. Create a TestPlan
2. Add a Test Execution with Tests, preconditions and/or and precondition iterations and create a TestRun
3. Try to export Test Run details starting the export from the Test Plan

Actual result/Attachments
it exports the following mappings blank: ${TestExecutions[n].TestRuns[a].Started On}
${TestExecutions[n].TestRuns[a].Finished On}

Expected result
Template exported