Metamorph: make certain that the reader is closed when openBytes returns

In most cases, this won't make much of a difference, but when reading
planes out of order it prevents files from being left open.
merge dev_4_4 -D org -I include -E exclude: PR 746 (CellWorx: ignore thumbnails and missing channel names)
merge dev_4_4 -D org -I include -E exclude: PR 789 (Metamorph: make certain that the reader is closed when openBytes returns)