NullPointerException when registering follow-up blood

[Nicklas Nordborg]

This seems to happing if a CASE is linked to at least two SPECIMENT or NOSPECIMEN items and at least one of them has a missing sampling date.

It is probably a rare situation that is probably only ever going to occur when testing because then it is more likely to not fill in all information.

java.lang.NullPointerException
	at java.util.Date.getMillisOf(Unknown Source)
	at java.util.Date.compareTo(Unknown Source)
	at java.util.Date.compareTo(Unknown Source)
	at java.util.ComparableTimSort.countRunAndMakeAscending(Unknown Source)
	at java.util.ComparableTimSort.sort(Unknown Source)
	at java.util.ComparableTimSort.sort(Unknown Source)
	at java.util.Arrays.sort(Unknown Source)
	at java.util.Collections.sort(Unknown Source)
	at net.sf.basedb.reggie.servlet.BloodFollowUpRegistrationServlet.getCaseOption(BloodFollowUpRegistrationServlet.java:368)
	at net.sf.basedb.reggie.servlet.BloodFollowUpRegistrationServlet.doGet(BloodFollowUpRegistrationServlet.java:272)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
....

The problem is the servlet add all dates (including nulls) to a list and then tries to sort it. The sorting doesn't work with null values.

[Nicklas Nordborg]

(In [2634]) Fixes #626: NullPointerException? when registering follow-up blood

Skip null operation dates when adding to the list.