fixed setting SiteLogoPath to a missing asset causing server errors

[Oaphi]

closes #2034

To reproduce on develop, set the SiteLogoPath site setting to a path starting with /assets/ and pointing to a non-existent asset (any gibberish should be fine). Observe a server error upon visiting, for example, <your origin here>/ca/posts/random.png (will attempt to generate a community ad for a random post). With the PR applied doing the latter should result in a valid image response with the community name instead of the logo.

Example community ad with a valid logo path:

And the same ad with an invalid logo path:

[Oaphi]

Lacks tests and needs #2004 to be merged for the TypeScript check to be fixed, so I am keeping it as a draft for the time being

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.93%. Comparing base (7b6dfd1) to head (6f7f84c).
⚠️ Report is 4 commits behind head on develop.

Additional details and impacted files

Components	Coverage Δ
controllers	76.18% <ø> (ø)
helpers	85.37% <100.00%> (+0.28%)	⬆️
jobs	66.88% <ø> (ø)
models	93.04% <ø> (ø)
tasks	61.11% <ø> (ø)

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[cellio]

I reproduced the error on develop, switched to this branch and got the behavior described -- and then switched the logo back to what it had been, but I still get "dev community" instead of the logo in the ad. Does that happen for you too?

[Oaphi]

and then switched the logo back to what it had been, but I still get "dev community" instead of the logo in the ad

Have you cleared the cache with Rails.cache.clear afterwards?

[cellio]

Have you cleared the cache with Rails.cache.clear afterwards?

Ah. No I hadn't realized it was cached, and yes that fixed the issue.

[cellio]

Tested and LGTM. Someone more fluent in magick and our caching should review the code.

[Oaphi]

Ah. No I hadn't realized it was cached, and yes that fixed the issue.

Yea, ads are cached the moment they are created, so you have to reset either the whole cache or the corresponding key every time you change a dependency such as a site setting (we should probably add some plumbing to do expire the cache automatically in such cases)

[cellio]

(we should probably add some plumbing to do expire the cache automatically in such cases)

I would expect setting a new value to flush the cache entry, yeah. That's something we should look into, separately.