[Ruby] Arrow::Array#[out_of_range] returns nil

[asfimport]

Reporter: Kouhei Sutou / @kou
Assignee: Kouhei Sutou / @kou

PRs and other links:

• GitHub Pull Request #3666

_{Note: This issue was originally created as ARROW-4593. Please see the migration documentation for further details.}

[asfimport]

Yosuke Shiro / @shiro615:
Issue resolved by pull request 3666
#3666