Issue Summary

There's no error handling for invalid JS time format string being set, so any reports utilising this date format string (e.g. cumulative flow diagram) simply gets stuck on the loading spinner forever.

Steps to Reproduce

1. Set the JS date format (System Settings > General configuration > Advanced settings > jira.date.picker.javascript.format) to an invalid value like one used for Java date format instead (e.g. `dd/MMM/yy h:mm a`)
2. Load the cumulative flow diagram (which is a report that utilises this date format string).

Expected Results

Some sort of error handling either on the report or when trying to configure the date format string saying it's an invalid format string and link user to guide with valid formats (https://support.atlassian.com/jira-cloud-administration/docs/configure-the-look-and-feel-of-jira-applications/#Change-date-and-time-formats).

Actual Results

The report gets stuck on the loading spinner without any obvious errors.

Workaround

Update the date format to a valid format string.