nimble/controller: fix null pointer dereference
nimble/controller: fix null pointer dereference

X-Original-Commit: 8052a2202d5672b6aebd4a760e6253732262ac05

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