Not catching data size too large.

[raycarrick-ed]

Please complete the following fields as applicable:

What version of the DMPRoadmap code are you running? (e.g. v2.2.0) v3.1

Expected behaviour: Fill in Research Outputs tab, create a dataset, put in ridiculously large number for the size like 10,000,000 PB and it'll crash trying to save the integer. Shold give some sort of sensible error message

Actual behaviour: Generic failure 500 message.

Steps to reproduce: above