Bug 32566: Don't show "ILL request log" when IllLog is disabled

Bug 32566: Don't show "ILL request log" when IllLog is disabled

When the IllLog system preference is disabled there will be no
log to view and the log will always appear empty.

To test:
1) Activate the IllModule system preference
2) Install a backend (BLDSS or FreeForm) following the wiki instructions:
   https://wiki.koha-community.org/wiki/ILL_backends
3) Go to the ILL module and add a new request
4) The "ILL request log" entry in the toolbar should be visible
5) Turn off the IllLog system preference
6) Reload the page - the option should remain visible
7) Apply patch
8) Verify the link is now no longer visible after reload
9) Re-activate the IllLog
10) Verify the option now appears

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>