Chart does not render in the dashboard with console error: <rect> attribute y: Expected length, "NaN"

Issue:

After upgrading to TIBCO JasperReports® Server v7.9, the charts in our dashboard are not showing any data nor displaying any errors.

But when the chart is individually ran, it is showing the correct data. 

After enabling the browser dev console (F12), we can see the following error generated in the console:

commons.main.js:57 Error: <rect> attribute y: Expected length, "NaN".

Solution:

The cause of the issue is due the presence of only a subtitle in the chart. When only subtitle is given, it throws the error in the console.

The workaround is to add a Title to the Sub Title or use the Title instead of the Sub Title. 

The issue was reported as below defect which currently remains in an open status:

JS-60865: Presence of only subtitle for a highchart in a report does not render chart in dashboard