st/mesa: fix computing the lowest address for interleaved attribs

Ptr can be very well NULL, so when there are two arrays, with one having
offset 0 (and thus NULL Ptr), and the other having a non-zero offset,
the non-zero value is taken as minimum (because of !low_addr ? start ...).
On 32-bit systems, this somehow works. On 64-bit systems, it leads to crashes.

Signed-off-by: Marek Olšák <maraeo@gmail.com>
1 file changed