ocfs2: fix panic in failed foilio allocation

In the Linux kernel, the following vulnerability has been resolved:

ocfs2: fix panic in failed foilio allocation

commit 7e119cff9d0a ("ocfs2: convert w_pages to w_folios") and commit

9a5e08652dc4b ("ocfs2: use an array of folios instead of an array of

pages") save -ENOMEM in the folio array upon allocation failure and call

the folio array free code.

The folio array free code expects either valid folio pointers or NULL.

Finding the -ENOMEM will result in a panic. Fix by NULLing the error

folio entry.