Attachments not getting attached when jira.issue.editable is used in the incoming workflow step

Issue Summary

Attachment can't be attached in a transition screen prior to a status with jira.issue.editable property set to FALSE.

Steps to Reproduce

1. In a workflow, set jira.issue.editable property to FALSE in a step (not transition) e.g. In Progress.
2. For the transition going into the In Progress step, make sure it uses a screen.
3. Go into any issue using the configured workflow and use the transition going into In Progress.
4. Add an attachment in the transition screen and have its thumbnail in the comment on the screen.
5. Transition the issue and observe if the attachment gets attached to the issue.

Expected Results

Attachments should be attached during the transition as the property shouldn't be in effect yet until the issue is in In Progress.

Actual Results

Attachments are shown to be attached but after the issue transitioned, none are there.

Workaround

Use other properties to restrict the user from editing the issue e.g. jira.permission.edit.user.