[gcc r13-549] [Ada] Restore defensive guard in checks for volatile actuals

[Pierre-Marie de Rodat <pmderodat@gcc.gnu.org>]

https://gcc.gnu.org/g:33400df641d834ca3fd3f2c964ed92759f128ffa

commit r13-549-g33400df641d834ca3fd3f2c964ed92759f128ffa
Author: Piotr Trojanek <trojanek@adacore.com>
Date:   Wed Mar 30 12:00:20 2022 +0200

    [Ada] Restore defensive guard in checks for volatile actuals
    
    When flagging names of volatile objects occurring in actual parameters
    it is safer to guard against identifiers without entity. This is
    redundant (because earlier in the resolution of actual parameters we
    already guard against actuals with Any_Type), but perhaps such
    identifiers will become allowed in constructs like:
    
       Subprogram_Call
         (Actual =>
            (declare
               X : Boolean := ...
                 with Annotate (GNATprove, ...)));
                                ^^^^^^^^^
    
    which include an identifier that does not denote any entity.
    
    Code cleanup related to handling of volatile components; behaviour is
    unaffected.
    
    gcc/ada/
    
            * sem_res.adb (Flag_Effectively_Volatile_Objects): Restore
            redundant guard.

Diff:
---
 gcc/ada/sem_res.adb | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/gcc/ada/sem_res.adb b/gcc/ada/sem_res.adb
index 12735daab6d..33f445d69b9 100644
--- a/gcc/ada/sem_res.adb
+++ b/gcc/ada/sem_res.adb
@@ -3873,7 +3873,8 @@ package body Sem_Res is
                   --  selector_name in selected_component or as a choice in
                   --  component_association.
 
-                  if Is_Object (Id)
+                  if Present (Id)
+                    and then Is_Object (Id)
                     and then Ekind (Id) not in E_Component | E_Discriminant
                     and then Is_Effectively_Volatile_For_Reading (Id)
                     and then