Initialize the output variables in the called function.

It was previously inconsistent, with partial initialization
outside and partial initialization inside.

Noted by Frediano Ziglio.
Acked-by: Frediano Ziglio <fziglio@redhat.com>

src/display.c

@@ -610,6 +610,8 @@ int display_scan_whole_screen(display_t *d, int num_vertical_tiles, int num_hori
     shm_image_t *fullscreen_new;
 
     memset(tiles, 0, sizeof(**tiles) * num_vertical_tiles * num_horizontal_tiles);
+    memset(tiles_changed_in_row, 0, sizeof(*tiles_changed_in_row) * num_vertical_tiles);
+
     fullscreen_new = create_shm_image(d, 0, 0);
     if (!fullscreen_new)
         return 0;

src/scan.c

@@ -361,8 +361,6 @@ static void scan_full_screen(scanner_t *scanner)
     int tiles_changed_in_row[num_vertical_tiles];
     int tiles_changed[num_vertical_tiles][NUM_HORIZONTAL_TILES];
 
-    memset(tiles_changed_in_row, 0, sizeof(tiles_changed_in_row));
-
     rc = display_scan_whole_screen(&scanner->session->display,
                                    num_vertical_tiles, NUM_HORIZONTAL_TILES,
                                    tiles_changed, tiles_changed_in_row);