Bug/5074 - Fix errors if Tag Manager is disabled via `googlesitekit_available_modules`

[hussain-t]

Summary

Addresses issue:

• #5074

Relevant technical choices

PR Author Checklist

• [x] My code is tested and passes existing unit tests.
• [ ] My code has an appropriate set of unit tests which all pass.
• [ ] My code is backward-compatible with WordPress 4.7 and PHP 5.6.
• [ ] My code follows the WordPress coding standards.
• [ ] My code has proper inline documentation.
• [x] I have added a QA Brief on the issue linked above.
• [x] I have signed the Contributor License Agreement (see https://cla.developers.google.com/).

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Code Reviewer Checklist

• [ ] Run the code.
• [ ] Ensure the acceptance criteria are satisfied.
• [ ] Reassess the implementation with the IB.
• [ ] Ensure no unrelated changes are included.
• [ ] Ensure CI checks pass.
• [ ] Check Storybook where applicable.
• [ ] Ensure there is a QA Brief.

Merge Reviewer Checklist

• [ ] Ensure the PR has the correct target branch.
• [ ] Double-check that the PR is okay to be merged.
• [ ] Ensure the corresponding issue has a ZenHub release assigned.
• [ ] Add a changelog message to the issue.

[github-actions[bot]]

Size Change: +2.25 kB (0%)

Total Size: 1.52 MB

Filename	Size	Change
./dist/assets/js/googlesitekit-activation-********************.js	28.6 kB	+215 B (+1%)
./dist/assets/js/googlesitekit-adminbar-********************.js	36.7 kB	+85 B (0%)
./dist/assets/js/googlesitekit-api-********************.js	9.29 kB	+2 B (0%)
./dist/assets/js/googlesitekit-datastore-forms-********************.js	8.97 kB	-2 B (0%)
./dist/assets/js/googlesitekit-datastore-location-********************.js	2.08 kB	-1 B (0%)
./dist/assets/js/googlesitekit-datastore-site-********************.js	15.2 kB	+5 B (0%)
./dist/assets/js/googlesitekit-datastore-ui-********************.js	9.07 kB	-1 B (0%)
./dist/assets/js/googlesitekit-datastore-user-********************.js	22.8 kB	+12 B (0%)
./dist/assets/js/googlesitekit-entity-dashboard-********************.js	65.6 kB	+170 B (0%)
./dist/assets/js/googlesitekit-idea-hub-post-list-********************.js	26.4 kB	+100 B (0%)
./dist/assets/js/googlesitekit-main-dashboard-********************.js	75.7 kB	+339 B (0%)
./dist/assets/js/googlesitekit-modules-********************.js	20.1 kB	-20 B (0%)
./dist/assets/js/googlesitekit-modules-adsense-********************.js	69.2 kB	-7 B (0%)
./dist/assets/js/googlesitekit-modules-analytics-4-********************.js	19.2 kB	+7 B (0%)
./dist/assets/js/googlesitekit-modules-analytics-********************.js	71.3 kB	+523 B (+1%)
./dist/assets/js/googlesitekit-modules-idea-hub-********************.js	28 kB	+12 B (0%)
./dist/assets/js/googlesitekit-modules-optimize-********************.js	19.8 kB	-32 B (0%)
./dist/assets/js/googlesitekit-modules-pagespeed-insights-********************.js	18.4 kB	-5 B (0%)
./dist/assets/js/googlesitekit-modules-search-console-********************.js	38.6 kB	-6 B (0%)
./dist/assets/js/googlesitekit-modules-tagmanager-********************.js	32.4 kB	-6 B (0%)
./dist/assets/js/googlesitekit-modules-thank-with-google-********************.js	26.7 kB	+401 B (+2%)
./dist/assets/js/googlesitekit-settings-********************.js	51.3 kB	+113 B (0%)
./dist/assets/js/googlesitekit-splash-********************.js	70.7 kB	+108 B (0%)
./dist/assets/js/googlesitekit-user-input-********************.js	45.7 kB	+123 B (0%)
./dist/assets/js/googlesitekit-vendor-********************.js	331 kB	+2 B (0%)
./dist/assets/js/googlesitekit-widgets-********************.js	16.4 kB	+1 B (0%)
./dist/assets/js/googlesitekit-wp-dashboard-********************.js	60 kB	+108 B (0%)

ℹ️ View Unchanged

Filename	Size
./dist/assets/css/googlesitekit-admin-css-********************.min.css	48.5 kB
./dist/assets/css/googlesitekit-adminbar-css-********************.min.css	11.1 kB
./dist/assets/css/googlesitekit-wp-dashboard-css-********************.min.css	5.97 kB
./dist/assets/js/31-********************.js	2.8 kB
./dist/assets/js/32-********************.js	2.28 kB
./dist/assets/js/33-********************.js	3.72 kB
./dist/assets/js/34-********************.js	51.9 kB
./dist/assets/js/35-********************.js	16.1 kB
./dist/assets/js/36-********************.js	70.9 kB
./dist/assets/js/37-********************.js	31.6 kB
./dist/assets/js/38-********************.js	3.12 kB
./dist/assets/js/analytics-advanced-tracking-********************.js	769 B
./dist/assets/js/googlesitekit-base-********************.js	1.13 kB
./dist/assets/js/googlesitekit-data-********************.js	2.12 kB
./dist/assets/js/googlesitekit-i18n-********************.js	3.92 kB
./dist/assets/js/googlesitekit-idea-hub-notice-********************.js	45.1 kB
./dist/assets/js/googlesitekit-polyfills-********************.js	379 B
./dist/assets/js/runtime-********************.js	1.34 kB

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[asvinb]

Thanks @hussain-t ! LGTM!