FWIW, all the [`else` block in question](https://searchfox.org/mozilla-central/rev/9e3413f54ed6c9165b5659558091d766d34a731f/dom/file/FileReader.cpp#308-331) seems to not be executed in out automated test environment neither, as per searchfox' coverage instrumentation.
Bug 1826666 Comment 1 Edit History
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FWIW, all the [`else` block in question](https://searchfox.org/mozilla-central/rev/9e3413f54ed6c9165b5659558091d766d34a731f/dom/file/FileReader.cpp#308-331) seems to not be executed in our automated test environment neither, as per searchfox' coverage instrumentation.