slapd terminates abnormally by segmentation fault in syncprov_matchops().

Issue

Systems are using Multi-Master replication. A slapd terminated abnormally by segmentation fault on a replicated system when many LDAP entries were deleted on a system. Here is the backtrace from core:

(gdb) bt
#0  0x00007fea393f1b6f in syncprov_matchops (op=0x7fea1f7fd310, opc=0x7fea140009c0, saveit=1) at ../../../../servers/slapd/overlays/syncprov.c:1309
#1  0x00007fea393f1f92 in syncprov_op_mod (op=0x7fea1f7fd310, rs=<value optimized out>) at ../../../../servers/slapd/overlays/syncprov.c:2075
#2  0x00007fea3e2ca1ea in overlay_op_walk (op=0x7fea1f7fd310, rs=0x7fea1f7fca80, which=op_modify, oi=0x7fea3ea71ac0, on=0x7fea3ea72370)    at ../../../servers/slapd/backover.c:659
#3  0x00007fea3e2cad2b in over_op_func (op=0x7fea1f7fd310, rs=<value optimized out>, which=<value optimized out>) at ../../../servers/slapd/backover.c:721
#4  0x00007fea3e2bf75f in syncrepl_updateCookie (si=0x7fea3ea72d60, op=<value optimized out>, syncCookie=0x7fea1f7fcee0) at ../../../servers/slapd/syncrepl.c:3186
#5  0x00007fea3e2c3f7b in do_syncrep2 (op=0x7fea1f7fd310, si=0x7fea3ea72d60) at ../../../servers/slapd/syncrepl.c:1245
#6  0x00007fea3e2c64ae in do_syncrepl (ctx=<value optimized out>, arg=0x7fea3ea3a580) at ../../../servers/slapd/syncrepl.c:1434
#7  0x00007fea3e25efd1 in connection_read_thread (ctx=0x7fea1f7fdb70, argv=<value optimized out>) at ../../../servers/slapd/connection.c:1247
#8  0x00007fea3e35e738 in ldap_int_thread_pool_wrapper (xpool=0x7fea3ea042a0) at ../../../libraries/libldap_r/tpool.c:685
#9  0x00007fea3c1f17f1 in start_thread () from /lib64/libpthread.so.0
#10 0x00007fea3bd2370d in clone () from /lib64/libc.so.6