Materializer crashes processing operations with pinned relations to non-existent views

[sandreae]

Test demonstrating the behaviour here: #177

[sandreae]

Instead of returning Ok(None) here as we should (and are now) we were critically failing the task when a document disn't exist for the passed document view.

aquadoggo/aquadoggo/src/materializer/tasks/reduce.rs

Lines 25 to 31 in f900374

	let document_id = match resolve_document_id(&context, &input).await? {
	Some(document_id) => Ok(document_id),
	None => {
	debug!("No document found for this view, exit without dispatching any other tasks");
	return Ok(None);
	}
	}?;

[sandreae]

It's fixed in the above PR.