Prevent error on views session retrieving

setting latest patch to NR and hiding duplicate and #3

patch #4 is working for me, thanks

Thanks for reporting.

Will need a test case showing the issue as a next step.

Thanks for this - I found the patch from #4 fixed my issue, where the views UI preview was failing, with a "SessionNotFoundException: Session has not been set" exception. I didn't quite get to the very bottom of the issue, but it might have been to do with my page display having exposed filters, which would remember their last setting (i.e. using the session), plus several other attached displays which were set to inherit exposed filters whilst also using contextual filters that would always use a default argument. So a bit complicated - and it's entirely possible that's not relevant. But I did debug to the point of confirming that the last request on the request stack had a null session property. That's despite me being logged in as an admin, using the views UI. The views preview works by creating a new request object and then pushing it to the stack - perhaps that needs to include copying any session object over?

For the patch itself, it seems odd to spin up an empty session object, which won't be backed by an actual session, just so that there's an array to fall back on. Especially if $session->set() ends up getting called, as the data set won't end up in the actual saved session.