btrfs: send: check for inline extents in range_is_hole_in_parent()

In the Linux kernel, the following vulnerability has been resolved:

btrfs: send: check for inline extents in range_is_hole_in_parent()

Before accessing the disk_bytenr field of a file extent item we need to check if we are dealing with an inline extent. This is because for inline extents their data starts at the offset of the disk_bytenr field. So accessing the disk_bytenr means we are accessing inline data or in case the inline data is less than 8 bytes we can actually cause an invalid memory access if this inline extent item is the first item in the leaf or access metadata from other items.