binding: navigation: add missing read lock around afb_event_push()

Add missing read lock around event pushing from value that isn't
required to be cached.

Bug-AGL: SPEC-2880
Change-Id: I7aae2ec9df722fdefcec2d35977251e008375d92
Signed-off-by: Matt Ranostay <matt.ranostay@konsulko.com>

binding/navigation-api.c

@@ -146,12 +146,22 @@ static void broadcast(afb_req_t request, const char *name, gboolean cache)
 		json_object_get(jresp);
 		*storage = jresp;
 
+		// increment reference for event
+		json_object_get(jresp);
+		afb_event_push(event, jresp);
+
 		g_rw_lock_writer_unlock(&ns->rw_lock);
+
+		return;
 	}
 
+	g_rw_lock_reader_lock(&ns->rw_lock);
+
 	// increment reference for event
 	json_object_get(jresp);
 	afb_event_push(event, jresp);
+
+	g_rw_lock_reader_unlock(&ns->rw_lock);
 }
 
 static void broadcast_status(afb_req_t request)