Bug 37005: Fix problem with item_type_description being undefined

Bug 37005: Fix problem with item_type_description being undefined

To test:
1. Set noItemTypeImages to 'Don't show'
2. Find a record with items and notice the holdings table never loads.
3. APPLY patch, maybe clear borwser cache too.
4. Try again, the holdings table should load.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Matt Blenkinsop <matt.blenkinsop@ptfs-europe.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>