Space export may export multiple spaces (regression)

Issue Summary

Sometimes, a content on space A might be pointing to a parent page from space B.
In that case, performing a XML space export for space A will include the space B.

Steps to Reproduce

1. Access a space that contains contents pointing to a parent page from another space
2. Export that space to XML
3. Import it to another instance

Expected Results

The export should include only a single space

Actual Results

The export will contain entries for two spaces, importing both on the new instance.

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available