Cursor disappears in fullscreen Xinha field

When a Xinha field is made fullscreen, the cursor disappears. The cursor then stays hidden (even when disabling fullscreen again) until the document is saved and the field is re-opened for editing.

Steps to reproduce:
1. click on a Xinha field to edit it
2. click the "fullscreen" button

Expected behavior: the cursor stays visible
Actual behavior: the cursor disappears