We were very inconsistent regarding these rules.
Personally I prefer no empty lines around blocks, clases, etc... as
recommended by the Ruby style guide [1], and they're the default values
in rubocop, so those are the settings I'm applying.
The exception is the `private` access modifier, since we were leaving
empty lines around it most of the time. That's the default rubocop rule
as well. Personally I don't have a strong preference about this one.
[1] https://rubystyle.guide/#empty-lines-around-bodies
When `valuator_group` was `nil`, `[valuator_group&.investment_ids]` is
evaluated to `nil`, and so we were adding an extra element to the array.
We could add a `compact` call to the resulting array, but I find it
easier to convert `nil` to an array using `to_a`.
