Bluetooth: Fix LE Pairing on previous connections

There was a crashing issue when pairing was performed on LE connections
that were already up, due to a NULL function pointer being followed.

Signed-off-by: Brian Gix <bgix@codeaurora.org>
diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c
index 8b2a92e..9089e65 100644
--- a/net/bluetooth/smp.c
+++ b/net/bluetooth/smp.c
@@ -973,7 +973,8 @@
 	}
 
 	if (hcon->out || rsp->resp_key_dist) {
-		hcon->disconn_cfm_cb(hcon, 0);
+		if (hcon->disconn_cfm_cb)
+			hcon->disconn_cfm_cb(hcon, 0);
 		hci_conn_put(hcon);
 	}