layers: Handle indirection in param_checker
layers: Handle indirection in param_checker

Code was being generated for param_checker that looked like:
  validate_pointer(pAllocInfo);
  validate_array(pAllocInfo->count, array);
Where validate_array could dereference a NULL pointer.  The code
generator was updated to insert NULL checks for this case:
  validate_pointer(pAllocInfo);
  if (pAllocInfo != NULL) {
      validate_array(pAllocInfo->count, array);
  }

Change-Id: I1eda66530dbff2e95d604a20d122179be172bedf

KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools