I see a NullPointerException when selecting mean series for an obs tool plugin.
I saw this when invoking the P/L distance calculator.
This also occurs with DCDFT currently!
I was able to replicate this by loading some data from a flat file then clicking the icon with the tooltip "DC DFT with Period Range" then select Means in the dialog and click ok.
This is because in Mediator.java the function performPeriodAnalysis these lines
List<ValidObservation> obs = getLatestNewStarMessage()
return null for (I assume) type means. obs then being null propagates down into lower level of the worker thread finally being accessed in the TSBase.java constructor throwing because of this line:
int sz = observations.size() + 1;
Fixed in 2.15.1