Continuation of bug 1249288. We expect nulls for some set of conditions (see [1]) but it's not clear if we're getting more than we should expect (~1%). The search engine retrieval code is a bit complex, which is why we haven't looked into this sooner. See https://bugzilla.mozilla.org/show_bug.cgi?id=1249288#c65 and subsequent comments. [1]: https://gecko.readthedocs.org/en/latest/toolkit/components/telemetry/telemetry/core-ping.html#defaultsearch

fwiw, if the numbers are insignificant, for now I think it's better for me to prioritize finishing the telemetry work rather than nailing this down. Also, Sebastian or Margaret might have better context on this code and when the search engines are null so it could be more efficient for them to look into the issue.

We're going to validate this against release and if the numbers don't look too bad, we'll close this. fwiw, the code to retrieve the search engine is very difficult to follow – it grabs the engine asynchronously, sometimes getting it from over the air, making it hard to figure out where the null might be coming from which is why I'm inclined to sweep it under the rug if the numbers are insignificant. (Practically, I assume it's null when the over-the-air search engine has come in in time, but the docs say we can return null in many places so...) NI Georg since we're waiting on release data validation.

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