Handle unknown browser detection gracefully.

[dd32]

Handle unknown browser detection gracefully when older versions of User_Agent_Info is loaded (eg. another plugin).

Fixes #45784

100% untested, assumptions made, no changelog included (merger to do so if required)

Proposed changes:

• Checks that the method exists in the loaded class before using it.

Other information:

• Have you written new tests for your changes, if applicable?
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Jetpack product discussion

Does this pull request change what data or activity we track or use?

Testing instructions:

• Untested.

[github-actions]

Are you an Automattician? Please test your changes on all WordPress.com environments to help mitigate accidental explosions.

• To test on WoA, go to the Plugins menu on a WoA dev site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin (Jetpack), and enable the fix/45784-User_Agent_Info-fatal branch.
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bin/jetpack-downloader test jetpack fix/45784-User_Agent_Info-fatal

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[jp-launch-control]

Code Coverage Summary

Coverage changed in 1 file.

File	Coverage	Δ%	Δ Uncovered
projects/packages/forms/src/contact-form/class-feedback.php	651/685 (95.04%)	0.01%	0 💚

Full summary · PHP report · JS report

[vianasw]

While I understand these changes in the context of the recent issue, it opens the door to keep adding method_exists checks whenever we add a new method to device-detection (if we remember to). I'm not sure I like this idea, given that the issue happened in combination with a legacy plugin that we encourage users to migrate from.

[dd32]

Closing in favour of the other options looked at via #45784 - making it so WPSC doesn't conflict with JP in future.