[node:term] bug in pre-taxonomy submit node code

$node->taxonomy comes in two formats:

[obj mode]
An array with keys of the term id and values of term objects

or

[preview mode]
An array with keys of the vocabulary id and values of:
term id for single select
array of term id for multi-select
array of free terms if key is 'tags'

The code that was trying to handle the preview mode was not working right (casting term id into an object).

This patch will check to see if the value in the term is an object, if it is it will do what it did before, if it isn't then then it handles preview mode correctly.