induced condenser treats null values different from regular condensers

[Dimitar Misev]

In regular condense and shorthand condensers like avg_cells, null values are ignored (cf. ​documentation).

In the induced condenser this is not the case: null values are treated the same way as in binary induced operation, i.e. the result is null if any cell in the operands (or slices in induced condenser) is null (cf. ​documentation).

With an example, these two expressions are equivalent and hence null value treatment is the same:

select condense +
       over i in [0:1]
       using coll3d[ i[0], 0:100, 0:100 ]
from coll3d

=

select coll3d[0, 0:100, 0:100] + 
       coll3d[1, 0:100, 0:100]
from coll3d

The correct equivalence of the first condense expression, however, should be:

select marray i in [0:100, 0:100]
       values add_cells( coll3d[ 0:1, i[0], i[1] ] )
from coll3d