Make gcc happy about dangling pointer

GCC is emitting a warning about a possible danling pointer on table
like definitions:

warning: possibly dangling reference to a temporary [-Wdangling-reference]
  660 |         auto const& table = get_current_events_table(state_indexes{});
      |                     ^~~~~

Which I think that really comes from the use of state_indexes{} as
argument:

  note: the temporary was destroyed at the end of the full expression
  660 |         auto const& table = get_current_events_table(state_indexes{});
      |                             ~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~

Clang is quiet about this and make me think that is a false positive
since the metaprogramming code is using just the type of the state_indexes
as much as I can see.

Signed-off-by: Jose Luis Rivero <[email protected]>

src/systems/elevator/vender/afsm/include/afsm/detail/transitions.hpp

@@ -525,7 +525,8 @@ class state_transition_table {
     void
     check_default_transition()
     {
-        auto const& ttable = transition_table<none>( state_indexes{} );
+        auto st = state_indexes{};
+        auto const& ttable = transition_table<none>( st );
         ttable[current_state()](*this, none{});
     }
 
@@ -544,15 +545,17 @@ class state_transition_table {
     void
     exit(Event&& event)
     {
-        auto const& table = exit_table<Event>( state_indexes{} );
+        auto st = state_indexes{};
+        auto const& table = exit_table<Event>( st );
         table[current_state()](states_, ::std::forward<Event>(event), *fsm_);
     }
 
     template < typename Event >
     actions::event_process_result
     process_transition_event(Event&& event)
     {
-        auto const& inv_table = transition_table<Event>( state_indexes{} );
+        auto st = state_indexes{};
+        auto const& inv_table = transition_table<Event>( st );
         return inv_table[current_state()](*this, ::std::forward<Event>(event));
     }
 
@@ -655,10 +658,11 @@ class state_transition_table {
     event_set
     current_handled_events() const
     {
-        auto const& table = get_current_events_table(state_indexes{});
+        auto st = state_indexes{};
+        auto const& table = get_current_events_table(st);
         auto res = table[current_state_](states_);
         auto const& available_transitions
-                            = get_available_transitions_table(state_indexes{});
+                            = get_available_transitions_table(st);
         auto const& trans = available_transitions[current_state_];
         res.insert( trans.begin(), trans.end());
         return res;
@@ -667,7 +671,8 @@ class state_transition_table {
     event_set
     current_deferrable_events() const
     {
-        auto const& table = get_current_deferred_events_table(state_indexes{});
+        auto st = state_indexes{};
+        auto const& table = get_current_deferred_events_table(st);
         return table[current_state_](states_);
     }