fix: Allow window to be truly undefined

[benjackwhite]

Changes

Follow up to #894 makes window and document actually maybe undefined so that we can check the types correctly instead of casting

Checklist

• Tests for new code (see advice on the tests we use)
• Accounted for the impact of any changes across different browsers

[github-actions]

Size Change: +3.85 kB (+1%)

Total Size: 739 kB

Filename	Size	Change
dist/array.full.js	175 kB	+978 B (+1%)
dist/array.js	117 kB	+899 B (+1%)
dist/es.js	117 kB	+899 B (+1%)
dist/exception-autocapture.js	12 kB	+56 B (0%)
dist/module.js	117 kB	+899 B (+1%)
dist/recorder-v2.js	104 kB	+46 B (0%)
dist/recorder.js	58.4 kB	+30 B (0%)
dist/surveys.js	39.9 kB	+43 B (0%)

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