Switch pages before removing current page

If we are asked to remove the current page, we should first switch to a
different page.

ocarina/body.py

@@ -82,6 +82,8 @@ def remove_page(name):
 	if page == None:
 		return
 	n = body.page_num(page)
+	if n == body.get_current_page():
+		body.set_current_page(n - 1)
 	body.remove_page(n)
 	del contents[name]