mesh: cfg_cli: Fix trying to write a NULL pointer
mesh: cfg_cli: Fix trying to write a NULL pointer

It's not always guaranteed that param->status will be non-NULL,
especially not after a subsequent patch to fix a race condition with
the response waiting.

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