get_post_meta fails to unserialize when $single=false

[andy]

When $single=false the return should be an array. maybe_unserialize is being applied to the array of rows so it doesn't do anything. It should be applied to each member of that array. Patch uses array_map and removes redundant logic.

If any plugin code is compensating by running maybe_unserialize on the array members, it will not be affected. If it uses unserialize, which is inadvisable anyway, it will break.

(In [8824]) maybe_unserialize the array members not the array when multple post meta items are returned. Fixes #7623 for trunk props andy.

Reopen for 2.6.2

(In [8825]) maybe_unserialize the array members not the array when multple post meta items are returned. Fixes #7623 for 2.6 branch props andy.