Comedian, TV host...man-eater? A source tells the new issue of UsWeekly (on stands now) that ChelseaHandler dumped 50Cent just before the holidays, leaving the 35-year-old rapper "heartbroken." Determined to win her back, 50 Cent -- who was first spotted canoodling with the Chelsea Lately host in October -- "spent Christmas sending her gifts, but she sent them back. She put a note on one that sai…