cr-dump: fix out-of-bounds write (OVERRUN)

CID 73381 (#1 of 1): Out-of-bounds write (OVERRUN)
15. overrun-local: Overrunning array loc_buf of 4096 bytes at byte offset 4096 using index len (which evaluates to 4096).

CID 73355 (#1 of 1): Out-of-bounds write (OVERRUN)
6. overrun-local: Overrunning array loc_buf of 4096 bytes at byte offset 4096 using index ret (which evaluates to 4096)