Memoizer: prevent exception if the memo file's version is not x.y.z

If the stored version is something like UNKNOWN, then minor version
parsing would have failed with a StringIndexOutOfBoundsException.

Fixes #11971.
Wlz: make the service variable transient

This prevents the Memoizer from storing the service variable, which
should prevent problems with reinitializing .wlz files when a memo file
is present.

Fixes #12019.
Merge pull request #990 from melissalinkert/rebased/develop/memo-fixes

Memoization fixes (rebased onto develop)