Set null values when subsets select non-materialized tiles

[Dimitar Misev]

In this example query, a subset intersects outside the sdom of the array. The outside part of the intersection is populated with 0s, but it should have null values (-10000 in this case).

$ rasql -q 'select encode((<[0:1,0:1] -9999.99f, -9999.99f; -1f, -1f> NULL VALUES [-10000:-9999.98]) [0:3,0:1], "csv")' --out string

Query result collection has 1 element(s):
  Result object 1: {-9999.99,-9999.99},{-1,-1},{0,0},{0,0}