Bug 21389: Correct Javascript error on article requests page

Bug 21389: Correct Javascript error on article requests page

Bug 21076 fixed a Javascript error on article requests page when patron is found.

There is also an error when patron is not found, with message :
  Patron not found
  No patron with this name, please, try another

This patch fixes by replacing TT condition by a JS condition testing the existance of the patron input.

Test plan:
1 - Do not apply patch
2 - Enable article requests
3 - Search on staff client and click 'Request article'
4 - Search for a patron that does not exist
5 - You get a yellow message "Patron not found"
6 - View error in console
7 - Apply patch
8 - Reload
9 - Not error is gone
10 - Search for a patron that does exist
11 - Check there is no error in console
12 - Check that autocompletion works

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>