prog: fix cheking nonoptional nil pointers in validation
prog: fix cheking nonoptional nil pointers in validation

Also update validation code to use arg.Type instead of passing typ recusively.

xairy/syzkaller,dotweiba/syzkaller,hyz0906/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller,zoulasc/syzkaller,hyz0906/syzkaller,google/syzkaller,zoulasc/syzkaller,zoulasc/syzkaller,dotweiba/syzkaller,google/syzkaller,xairy/syzkaller,google/syzkaller,xairy/syzkaller,google/syzkaller,dotweiba/syzkaller,hyz0906/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller,hyz0906/syzkaller,hyz0906/syzkaller,zoulasc/syzkaller,dotweiba/syzkaller,xairy/syzkaller