To say that the new Adam Sandler movie, "Blended", is better than some of his other recent work — "Jack and Jill", for example — isn't saying much. But there's something else disappointing about "Blended", which stars Sandler and Drew Barrymore (in their third collaboration) as single parents thrown together on an African family vacation. The fact is, there are actual sparks of sweetness, actual moments of tenderness, mostly thanks to Barrymore's sunny and grounded presence and the relaxed chemistry between the stars. But the moments don't stay sweet.