Accessing members of a null pointer is undefined behavior, even when
only used to obtain the address again. So use a non-zero value as the
base pointer address instead. 32 was chosen to provide sufficient
alignment guarantees.

Bug b/119823623

Change-Id: Ia6d24dd6c2740261948860c45eb35cc489a3a827
Reviewed-on: https://swiftshader-review.googlesource.com/c/22788Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>