small fixlet
Work around Safari XHR range caching bug

Safari sometimes returns the wrong cached chunk when fetching
requests with Range header; this seems much worse when seeking
around the file.

Upstream: https://bugs.webkit.org/show_bug.cgi?id=82672
Fixes: https://github.com/brion/ogv.js/issues/145
More aggressively die if stuck in loop or no codec data