Handle another edge case in Partition:-Simpl:-condition.
Handle another edge case in Partition:-Simpl:-condition.

This is relevant to #81; this check will be necessary when e.g.
all of the conjuncts of a condition to be solved are ones which
have been 'frozen' (and so Maple doesn't understand what they
are, and conservatively throws out the actual expression and
replaces it with garbage).

zachsully/hakaru,zachsully/hakaru