There is no reason to do separate image buffer release when there's
found buffer but with empty rects because of the following reasons:
- All the acquire() calls are followed with corresponding release()
calls, regardless of whether image buffer was empty, missing or
whatever.
- It was done wrong -- since lock was passed as NULL, it'll only
de-reference the image buffer itself, this causes following:
* Wrong user counter since there'll subsequent release() call with
the proper lock passed to it.
* Global locks are to be released prior to the spin locks,
and such an extra release violated this rule.
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