Fix missing nil check for control variable in formatter's base - Issue 6510

[ahasunos]

Description

This PR fixes the issue #6510; missing nil check for control variable in the Base class of Inspec::Formatters. This issue is only faced in InSpec 5 (inspec-5 branch).

It was fixed in InSpec 6 (now main branch) with the other work on the base and streaming reporters.

Related Issue

#6510 - Base InSpec formatter class missing nil check

inspec/lib/inspec/formatters/base.rb:163:in `block in statistics': undefined method `any?' for nil:NilClass (NoMethodError)

          skipped += 1 if control[:results].any? { |r| r[:status] == "skipped" }
                                           ^^^^^

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New content (non-breaking change)
• Breaking change (a content change which would break existing functionality or processes)

Checklist:

• I have read the CONTRIBUTING document.