fix(apng): Correct `info_rowbytes` in `png_read_reinit`

In the case where the application has not called `png_read_update_info`,
`png_ptr->info_rowbytes` is 0 and should not be updated.

In the case where the application has called `png_read_update_info`,
the value of `info_ptr->rowbytes` needs to be updated as well as
`png_ptr->info_rowbytes`, so that `png_get_rowbytes` works correctly.

Co-authored-by: Maarten Bent <MaartenBent@users.noreply.github.com>
Reviewed-by: Cosmin Truta <ctruta@gmail.com>
Signed-off-by: John Bowler <jbowler@acm.org>
Signed-off-by: Cosmin Truta <ctruta@gmail.com>

pngrutil.c

diff --git a/pngrutil.c b/pngrutil.c
index 83e380f..389591d 100644
--- a/pngrutil.c
+++ b/pngrutil.c
@@ -4928,7 +4928,7 @@
    png_ptr->height = info_ptr->next_frame_height;
    png_ptr->rowbytes = PNG_ROWBYTES(png_ptr->pixel_depth,png_ptr->width);
    if (png_ptr->info_rowbytes != 0)
-      png_ptr->info_rowbytes =
+      png_ptr->info_rowbytes = info_ptr->rowbytes =
          PNG_ROWBYTES(info_ptr->pixel_depth, png_ptr->width);
    if (png_ptr->prev_row)
       memset(png_ptr->prev_row, 0, png_ptr->rowbytes + 1);