Starting with Job Configuration History Plugin Version 1191.v168c8c2b_956a, when using the Job Config History menu item from Jenkins dashboard to view system config ($JENKINS/jobConfigHistory/history?name=config/)...  the Show Diffs button is missing and the Entries Per Page controls result in a blank page for any value other than the default (25) or when clicking Page forward(>)/back(<)/numbers buttons.

broken since: 1191.v168c8c2b_956a
last working version: 1187.v2a_b_1ca_54d18d

To reproduce the problem:

• navigate to Jenkns Dashboard main page
• select the Job Config History button from main menu
• from the resulting "All Configuration History" page, click one of the config (system) links
• on the resulting page, observe

1. Show Diffs button is missing from controls at bottom of page
2. click any Entries Per Page button other than 25 (the default) and observe blank page result with the message "No configuration history available"
3. click a page number other than 1 or use the next (>) or previous (<) buttons and observe a blank page with the message "No configuration history available"