Saving a copied page with attachments added to draft fails with NullPointerException

Steps to reproduce:

1. Copy a page.
2. When the editor appears for the new page, add a new image attachment.
3. Save the new page.

Fails with the following exception on CAC (2.7.2):

java.lang.NullPointerException
at com.atlassian.confluence.pages.actions.AbstractCreatePageAction.transferDraftAttachments(AbstractCreatePageAction.java:164)
at com.atlassian.confluence.pages.actions.AbstractCreatePageAction.doAdd(AbstractCreatePageAction.java:139)
at com.atlassian.confluence.pages.actions.CopyPageAction.doAdd(CopyPageAction.java:58)

And with the following on EAC (2.8-m7-r2):

java.lang.NullPointerException
at com.atlassian.confluence.pages.actions.AbstractCreatePageAction.transferDraftAttachments(AbstractCreatePageAction.java:186)
at com.atlassian.confluence.pages.actions.AbstractCreatePageAction.doAdd(AbstractCreatePageAction.java:147)
at com.atlassian.confluence.pages.actions.CopyPageAction.doAdd(CopyPageAction.java:58)