Setting Non-Working Day throws Error Message when System Default Format/Language is set to Croatian

When setting the system default language and time format to Croatian (Croatia), there is error message thrown (refer below)

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Details

        Exception: TypeError: Calendar._SDN is undefined
        Resource: http://localhost:8211/s/hr_HR-6oc9nx-418945332/854/3/eb2e1bc962af4a137d63c9ca02b68ec8/_/download/contextbatch/js/greenhopper-rapid-non-gadget,gh-rapid-config,atl.general/batch.js
        Line: 1

Environment
Mozilla/5.0 (Windows NT 6.1; WOW64; rv:20.0) Gecko/20100101 Firefox/20.0

Steps to Replicate

1. Set system default language and time format to "Croatian"
2. Create any type of rapidboard (Scrum/Kanban)
3. Click on the Tool at top right corner, and choose configure
4. Click on the Working Days tab
5. Add any date on the Non-Working Day
6. Navigate away from the configuration page
7. Return to configuration page, error noticed below

Additional Information

1. JIRA version 5.2.11 (latest) with GH 6.2 (latest)
2. Consistent error throughout IE9, Firefox, Chrome

Workaround

• Set the jvm to other language by setting the following Startup Properties

  -Duser.language=en
  -Duser.country=UK
  

• Set system default language to English (German also tested fine)