(produce): When player->simulation, level production executed item

(produce): When player->simulation, level production executed item
production code for item I_NONE.  This tries to put products into
vec[I_NONE].  Until item.h rev. 1.12, vec[I_NONE] was unused and zero,
so it worked.  Since then, it's a subscript out of bounds, clobbering
two bytes of stack.  The (unpredictable) stack contents could make the
code believe that there's not enough space for the `products', which
then reduced predicted production, typically to zero.