Fix vectorize bug
Fix vectorize bug

Scalarized allocations (e.g. inside if statements) were being vectorized
when loaded from but not vectorized when allocated, resulting in out-of-
bounds reads!

jiawen/Halide,kgnk/Halide,psuriana/Halide,kgnk/Halide,ronen/Halide,psuriana/Halide,kgnk/Halide,psuriana/Halide,ronen/Halide,ronen/Halide,jiawen/Halide,psuriana/Halide,kgnk/Halide,kgnk/Halide,ronen/Halide,psuriana/Halide,kgnk/Halide,ronen/Halide,jiawen/Halide,ronen/Halide,jiawen/Halide,kgnk/Halide,jiawen/Halide,kgnk/Halide,ronen/Halide,jiawen/Halide,psuriana/Halide,ronen/Halide,jiawen/Halide,psuriana/Halide