Deep stripping whitespace in nested search params with group conditions

[aukraine]

Resolves #1414

Fix case when strip_whitespace doesn't work with group conditions

Before

> User.ransack({g: [name_cont: "  John  ", email_cont: "  John ", m: "or"]}).result
=> []

After

> User.ransack({g: [name_cont: "  John  ", email_cont: "  John ", m: "or"]}).result
=> [#<User id, ...>]