chore: fix circle-env for contributor PRs

[flotwig]

• Closes #21211 broke the build for external contributors.  #21284

User facing changelog

n/a

Additional details

• Change in chore: add env var checking to verify-mocha-results #21211 didn't take into account contributor PRs.
• This PR ignores the env checking if Environment is empty (contributor PR)
• Example of this working: https://app.circleci.com/pipelines/github/cypress-io/cypress/37199/workflows/68edd3fc-5702-473e-bcfb-31a52b7d7857/jobs/1495506?invite=true#step-111-3

How has the user experience changed?

PR Tasks

• Have tests been added/updated?
• [na] Has the original issue (or this PR, if no issue exists) been tagged with a release in ZenHub? (user-facing changes only)
• [na] Has a PR for user-facing changes been opened in cypress-documentation?
• [na] Have API changes been updated in the type definitions?
• [na] Have new configuration options been added to the cypress.schema.json?

[cypress-bot]

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[cypress]

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Test summary

38949 • 1 • 465 • 4 • 9

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Run details

Project	cypress
Status	Failed
Commit	8702bd0
Started	May 2, 2022 3:34 PM
Ended	May 2, 2022 3:51 PM
Duration	16:45 💡
OS	Linux Debian - 10.10
Browser	Multiple

View run in Cypress Dashboard ➡️

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Failures

	cypress/integration/commands/files_spec.js		1
1	... > has implicit existence assertion, retries and throws a specific error when file does not exist for null encoding

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Flakiness

	e2e/origin/commands/actions.spec.ts		1
1	cy.origin actions > #consoleProps > .submit()
	settings_spec.js		1
1	Settings > file preference panel > loads preferred editor, available editors and shows spinner
	e2e/origin/commands/navigation.spec.ts		1
1	cy.origin navigation > .visit() > supports auth options and adding auth to subsequent requests
	cypress/proxy-logging_spec.ts		2
1	Proxy Logging > request logging > xhr log has response body/status code when xhr response is logged second
2	Proxy Logging > request logging > xhr log has response body/status code when xhr response is logged second
This comment includes only the first 5 flaky tests. See all 9 flaky tests in the Cypress Dashboard.

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