What happens if one of the players doesn't have a benched Pokemon when using Drifblim's "Take Away" attack?
There is no restriction on using the attack if there is no benched Pokemon. If a player has no Benched Pokemon, that player loses. If neither player has Benched Pokemon, then it is a tie and a game of Sudden Death must be played.
Source: Undaunted FAQ (2010-09-09), PUI Rules Team (2010-09-09)

Relevant cards

Note: All applicable cards may not be listed below.
HGSS3_12
WOTCGH_4