convert_delta: invalid memory read by default

[asarubbo]

~ $ convert_delta 
AddressSanitizer:DEADLYSIGNAL
=================================================================
==965==ERROR: AddressSanitizer: SEGV on unknown address 0x10012c4b9395 (pc 0x0000004c4122 bp 0x7ffd62609bc0 sp 0x7ffd62609ac0 T0)
==965==The signal is caused by a READ memory access.
    #0 0x4c4121 in main /var/tmp/portage/dev-util/diffball-1.0.1-r2/work/diffball-1.0.1/convert_delta.c:107:14
    #1 0x7f4c88702dca in __libc_start_main /var/tmp/portage/sys-libs/glibc-2.29-r2/work/glibc-2.29/csu/../csu/libc-start.c:308:16
    #2 0x41c4b9 in _start (/usr/bin/convert_delta+0x41c4b9)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /var/tmp/portage/dev-util/diffball-1.0.1-r2/work/diffball-1.0.1/convert_delta.c:107:14 in main
==965==ABORTING
Aborted