Completion never hit

I have been using this library for a month-ish now (it's 🔥🚒).

I recently found a bug where video trimming never completes. The progress reaches around 0.999874 and then the completion / error / cancel callbacks are not called.

My suspicion is that this is just an arithmetic error. To get around this I wrapped the callback in a suspending cancelable coroutine, and give the coroutine a timeout. Unfortunately that means I consider 0.9999848 a failure, but I imagine under the hood it actually succeeded.

Would be nice to fix this (:

No file, test, or entry point is named. Start by reproducing video trimming with progress near 0.999874 and trace the completion, error, and cancel callback paths; done means one of the expected callbacks is reliably invoked when trimming finishes.

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