r.in.pdal: fix integer overflow (OSGeo#2844)

Address integer overflow in call to Rast_set_null_value()
by instead looping over rows and set rows to NULL.

Solution by:
Co-authored-by: Markus Metz <markus.metz.giswork@gmail.com>

raster/r.in.pdal/point_binning.c

@@ -57,7 +57,10 @@ int blank_array(void *array, int nrows, int ncols, RASTER_MAP_TYPE map_type,
     case -1:
         /* fill with NULL */
         /* alloc for col+1, do we come up (nrows) short? no. */
-        Rast_set_null_value(array, nrows * ncols, map_type);
+        for (row = 0; row < nrows; row++) {
+            Rast_set_null_value(ptr, ncols, map_type);
+            ptr = G_incr_void_ptr(ptr, ncols * Rast_cell_size(map_type));
+        }
         break;
 
     default: