Handle app-compat environment check where self does not exist

[hsubox76]

Properly handle the case in app-compat checks where window exists but self does not. (This apparently occurs in Ionic Stencil's Jest preset.)

This is a safer check as isBrowser() now checks for the existence of window, so if it passes, the second condition shouldn't error.

Fixes #8365

[changeset-bot]

🦋 Changeset detected

Latest commit: 77fb068

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@firebase/app-compat	Patch
firebase	Patch

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[github-actions]

Changeset File Check ⚠️

• Warning: This PR modifies files in the following packages but they have not been included in the changeset file:%0A - @firebase/util%0A%0A Make sure this was intentional.

[google-oss-bot]

Size Report ¹

Affected Products

• @firebase/app-compat

  Type	Base (14b7720)	Merge (d1995c8)	Diff
  browser	5.28 kB	5.28 kB	+4 B (+0.1%)
  esm5	6.13 kB	6.14 kB	+4 B (+0.1%)
  main	6.73 kB	6.74 kB	+4 B (+0.1%)
  module	5.28 kB	5.28 kB	+4 B (+0.1%)

• firebase

  Type	Base (14b7720)	Merge (d1995c8)	Diff
  firebase-app-compat.js	31.7 kB	31.7 kB	+4 B (+0.0%)
  firebase-app.js	102 kB	102 kB	+175 B (+0.2%)
  firebase-compat.js	789 kB	789 kB	+4 B (+0.0%)
  firebase-performance-standalone-compat.js	70.6 kB	70.6 kB	+4 B (+0.0%)

Test Logs

• Base (14b7720): https://github.com/firebase/firebase-js-sdk/actions/runs/10000796698
• Merge (d1995c8): https://github.com/firebase/firebase-js-sdk/actions/runs/10012125604

1. https://storage.googleapis.com/firebase-sdk-metric-reports/sXzLYGneSq.html

[google-oss-bot]

Size Analysis Report ¹

Affected Products

No changes between base commit (14b7720) and merge commit (d1995c8).

Test Logs

• Base (14b7720): https://github.com/firebase/firebase-js-sdk/actions/runs/10000796698
• Merge (d1995c8): https://github.com/firebase/firebase-js-sdk/actions/runs/10012125604

1. https://storage.googleapis.com/firebase-sdk-metric-reports/gCslInIjC6.html