Error with mandatory input controls - JasperReports Server 7.8.0

[chinpokomonjasper]

I am seeing a really strange error with reports on JasperReports Server 7.8.0, where if the report contains a mandatory input control, the report will display this error when it's run:

 

This error only occurs if there is a mandatory input control added to the report, and can be consistently reproduced regardless of the report's content - the error occurs even when the report is blank. 

The data type of the input does not matter.   It could be text field or a date field – as long as it’s set as mandatory, the error will occur.   If the field is not mandatory, then there’s no error.

I've tested the same scenario on an earlier version of JRS (6.3.0) and the error does not occur there.

The corresponding stack trace from the server logs has been attached.

Any idea what could be causing this error?