Don't set min/max to Expr() in merge boxes
Don't set min/max to Expr() in merge boxes


Former-commit-id: 903b9cee0043b7a7b5e72dbd6d103597ee04fcde
Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide