fix(emqx_lwm2m_timer): Dialyzer warnings

apps/emqx_lwm2m/src/emqx_lwm2m_timer.erl

@@ -33,7 +33,7 @@
     logger:Level("LWM2M-TIMER: " ++ Format, Args)).
 
 cancel_timer(#timer_state{tref = TRef}) when is_reference(TRef) ->
-    erlang:cancel_timer(TRef), ok.
+    _ = erlang:cancel_timer(TRef), ok.
 
 refresh_timer(State=#timer_state{interval = Interval, message = Msg}) ->
     cancel_timer(State), start_timer(Interval, Msg).

apps/emqx_lwm2m/src/emqx_lwm2m_xml_object_db.erl

@@ -86,8 +86,8 @@ stop() ->
 %% ------------------------------------------------------------------
 
 init([]) ->
-    ets:new(?LWM2M_OBJECT_DEF_TAB, [set, named_table, protected]),
-    ets:new(?LWM2M_OBJECT_NAME_TO_ID_TAB, [set, named_table, protected]),
+    _ = ets:new(?LWM2M_OBJECT_DEF_TAB, [set, named_table, protected]),
+    _ = ets:new(?LWM2M_OBJECT_NAME_TO_ID_TAB, [set, named_table, protected]),
     PluginsEtcDir = emqx:get_env(plugins_etc_dir),
     DefBaseDir = re:replace(PluginsEtcDir, "plugins", "lwm2m_xml", [{return, list}]),
     BaseDir = application:get_env(emqx_lwm2m, xml_dir, DefBaseDir),