Consider this scenario:

    if params[:foo]
      conditions = { foo: true }
    end

    foos = Foo.where(conditions).order(:id)

When params[:foo] is nil, this would call:

    foos = Foo.where(nil).order(:id)

In this scenario, we want Foo.where(conditions) to be the same as calling
Foo.all, otherwise we'd get a "NoMethodError order for WhereChain".

Related to #8332.