When a patient is imported via JSON an empty PubmedID is not discarded

When a patient is imported via JSON an empty PubmedID is not discarded, resulting in a patient with an empty pubmedID (which can cause the same problem that is trying to fix)

Exporting as JSON should also be fixed to exclude empty pubmedIDs (even though supposedly none are possible now)

(this is lower priority than since it is less likely to happen)