Release Burndown is reporting an estimated issue closed without being assigned to a sprint

Issue Summary

When an issue is estimated and assigned to a version, if the issue is closed without being assigned for any sprint, it is incorrectly listed under one of the active sprints at the "Release Burndown" report.

This is a scope change and it should not be listed with the other planned issues for the sprint. The ideal is to list it under a separate section as an unplanned item.

Steps to Reproduce

• At the Admin> Applications> Jira Software configuration, check the option "Parallel Sprints"
• Have a project and board
• Define a Version for the Project "release1"
• Create Sprint 1 and Sprint 2
• Create some estimated Stories A, B, C, D and assign all of them to fix version "release1"
• Assign Story A to sprint 1 and start this Sprint
• Assign Story B to sprint 2 and start this Sprint
• On Sprint 1, complete issue A
• Observe the Report "Release Burndown" - It will incorrectly report the issue under "Sprint 2" (bug JSWSERVER-12616)
• On Sprint 2, complete issue B
• Observe the Report "Release Burndown" - It will show both issues under "Sprint 2" (bug JSWSERVER-12616)
• On Backlog, edit issue C and complete it

Expected Results

Issue "C" reported as completed but not assigned to any specific Sprint

Actual Results

Issue "C" was incorrectly showed under "Sprint 2", but Issue "C" was never planned for this sprint.

Workaround

Add validation to not allow an estimated issue that belongs to a Release to be closed without being assign to a sprint first.