-e: see title, they don't stop you from doing anything though

-repro:
--1) open attached project or make a new one
--2) add a scene to your build
--3) build for WebGL
--4) go to http://files.unity3d.com/build-report/
--5) click "understood"
--6) go to Stripping
--7) click "calculate size" and wait for it to finish
--8) go back to editor
--9) uncheck the scene from the build
--NOTICE exception being logged in the console (any selection/check/uncheck will throw same exception):
---"TLS Allocator ALLOC_TEMP_THREAD, underlying allocator ALLOC_TEMP_THREAD has unfreed allocations"