The history action as implemented by HistoryEntityAction does not handle the case of a non-existing page correctly. This causes a fatal error, for example:
https://www.wikidata.org/w/index.php?title=Q500000000&action=history
Version: unspecified
Severity: normal
URL: https://www.wikidata.org/w/index.php?title=Q500000000&action=history