`expose_nil:` conflicts with options passing to a block

[zverok]

Minimum reproducible example:

class Test < Grape::Entity
  expose(:a, expose_nil: false) { |obj, options| options[:a] }
end

pp Test.new({}, a: 1).as_json # expected {a: 1}, renders {}
pp Test.new({}, a: nil).as_json # expected {}, renders {}

More debugging shows that block always returns nil, because when expose_nil: is present, the content of options inside block is changed completely; which this debugging serializer shows:

class Test < Grape::Entity
   expose(:a) { |obj, options| p(simple: options); options[:a] }
   expose(:b, as: :d) { |obj, options| p(with_as: options); obj[:a] }

   expose(:c, expose_nil: false) { |obj, options| p(with_expose_nil: options); options[:a] }
end

pp Test.new({}, a: 1, b: 2, c: 3).as_json

It prints this values for options inside blocks (and yes, in this order):

{:with_expose_nil=>{:expose_nil=>false, :proc=>#<Proc:0x0000555bb661d9a8 test_grape_expose.rb:52>}}
{:simple=>#<Grape::Entity::Options:0x0000555bb661c210 @opts_hash={:a=>1, :b=>2, :c=>3, :attr_path=>[:a]}, @has_only=false, @has_except=false, @for_nesting_cache={}, @should_return_key_cache={}>}
{:with_as=>#<Grape::Entity::Options:0x0000555bb661c210 @opts_hash={:a=>1, :b=>2, :c=>3, :attr_path=>[:d]}, @has_only=false, @has_except=false, @for_nesting_cache={}, @should_return_key_cache={}>}

It seems that block in this case receives "options passed to expose DSL" instead of "options passed to serialization"?..