While loop which execute only max 1 times
Maybe here should be if instead while?
while (result->tile == NULL)
{
g_printerr ("NULL tile in %s %p %i %i %i %p\n", __FUNCTION__, result, result->x, result->y, result->z,
result->tile);
return NULL;
}
https://gitlab.gnome.org/GNOME/gegl/-/blob/master/gegl/buffer/gegl-tile-handler-cache.c#L483-488