nimble/host: fix find by address when addr is NULL
nimble/host: fix find by address when addr is NULL

Addr is NULL when sending le connection request using whitelist.
Error occurs on bsp/native when trying to do ble_addr_cmp
with NULL addr. There is segmentation fault when reading from NULL.

X-Original-Commit: 536fee4310fadeb5a10732cbbca67593bd22ae44

apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble