_write_pack_idx_v2: close idx_map separately
_write_pack_idx_v2: close idx_map separately

...in its own finally block, so that the idx_f close will be attempted
even if the idx_map close throws an exception.

Signed-off-by: Rob Browning <1dc5917c2adeeba13d1ef33dbb40691a1b67cc65@defaultvalue.org>
Tested-by: Rob Browning <1dc5917c2adeeba13d1ef33dbb40691a1b67cc65@defaultvalue.org>

gevaerts/bup,gevaerts/bup,gevaerts/bup,ToxicFrog/bup,gevaerts/bup,ToxicFrog/bup,gevaerts/bup,ToxicFrog/bup,ToxicFrog/bup,ToxicFrog/bup