NPE caused by deleted and redacted elements

[Simon Poole]

A history with deleted and redacted elements will cause a NPE when invoking the compare screen.

See https://www.openstreetmap.org/node/1/history for an example of this.

I would suggest that the current status of the element needs to be displayed in the comparison, that is visible/deleted and if the changeset was redacted.

[zohaib]

I think the reason was that I was passing the element with the list position instead of the actual version number, fixed it in this commit.

Need to test for the redacted changeset elements, haven't been able to recreate it