procmem: fix procmem crash issue

For the case pm_map_pagemap return error(e.g, maps[i]->start==maps[i]->end==0),
the main loop continue without set mis[i] fields, and then mis[i]==0. So that
the corresponding mi item is 0 for this case.
Skip dumping this item to avoid crash.

Change-Id: I7e1bea1abdccfd7594b9d904938b3462dc182a76
Signed-off-by: Hong-Mei Li <a21834@motorola.com>