hash_equals(): Expected $known_string to be a string, null given in Drupal\webp\Controller\ImageStyleDownloadController::deliver()

I see this error too. In some of our cases it looks like the image style that the module it's trying to serve is missing. So maybe just having a more friendly way to exit out in case of missing file. I edited the first patch a bit and now I get Error generating image, missing source file. message instead of the site Temporarily Unavailable message.

Since the switch to PHP 8.1 I had the same error, patch #6 fixed it successfully in my case.

RTBC for #6.

Patch #6 doesn't adhere to the Drupal code style. Needs a slight update.

@jedgar1mx see https://www.drupal.org/docs/develop/standards/coding-standards

Made some fixes on the formatting of #6. Now it should be ok.

#12 looks good, status back to RTBC

Patch #12 didn't apply via composer patching. New patch also fixes bad code style (tabs) in next few lines.

+      try {
+        if (isset($image_token)) {
+          $valid &= hash_equals($request->query->get(IMAGE_DERIVATIVE_TOKEN), $image_style->getPathToken($image_uri));
+        }
+        else {
+          $valid = false;
+        }
+      }
+      catch (\Throwable $th) {
+        $valid = false;
+      }

There is no need to use a try block. It's sufficient to avoid to pass NULL to hash_equals().

For changing the code to follow the coding standards, a new issue is required.

New patch with feedback from #15 included.

The logic in the controller can probably otherwise be streamlined a bit, but I think this patch addresses the issue and has the smallest diff.

Patch in #17 applies properly and solves the error.

Patch #17 solved the issue

+1 patch#17

+1, Patch 17 solves the issue.

Patch #17 solved the issue

Looks good (patch #17 fixes the issue), hope this gets into a release soon :)

Well .. patch #17 what do we could have done without you? :D

17 is required for me or the site fails, adding 17 works though!

@mandclu asked for confirmations of open issues on #3290669 so we can get a new stable release, so here is another confirmation this is RTBC and working on our websites :)

I can confirm again #17 works fine on multiple production sites and this issue seems RTBC and for release

Thanks to all for the various patches, as well as feedback on the patch in #17. Merged in, and will roll a release shortly.