Space key is lost when editing link

While editing an existing link to a page at different space, the space key is lost in the "Link" text field.

How to reproduce:

• Create a link to a page at different space (e.g. KEY:Page#Headings)
• Link to "Headings" section is valid and editable
• Edit the link to make a change (e.g. change the Link Text)

Result: The space key is lost. After closing the dialog, the link is no longer valid and uneditable.

Expected result: The space key is preserved and the link remains valid and still editable after closing the dialog.

Environment: Firefox 26, IE 10

See attached screenshot.