Google indexing survey urls with a 500 error

Google has started indexing urls like the following:

https://www.mysite.com/index.php?option=com_communitysurveys&view=surveys&layout=modal&tmpl=component&1a2e41504134f34e71fa07758ca5f0fa=1

and then reporting them as server 500 errors to be fixed.

Any ideas where they're finding these url's and how I stop them indexing them?

Thank you, John