[Ada] Fix latent bug in set_end_locus_from_node

[Pierre-Marie de Rodat via Gcc-patches]

Avoid calling End_Label on the Empty node.

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

        * gcc-interface/trans.c (set_end_locus_from_node): Check that
        Handled_Statement_Sequence is not Empty before calling
        End_Label, because the Empty node has no End_Label, and
        depending on the exact node layout chosen by gen_il, calling
        End_Label might crash, or might work OK by accident.
diff --git a/gcc/ada/gcc-interface/trans.c b/gcc/ada/gcc-interface/trans.c
--- a/gcc/ada/gcc-interface/trans.c
+++ b/gcc/ada/gcc-interface/trans.c
@@ -10507,10 +10507,15 @@ set_end_locus_from_node (tree gnu_node, Node_Id gnat_node)
     case N_Package_Body:
     case N_Subprogram_Body:
     case N_Block_Statement:
-      gnat_end_label = End_Label (Handled_Statement_Sequence (gnat_node));
+      if (Present (Handled_Statement_Sequence (gnat_node)))
+	gnat_end_label = End_Label (Handled_Statement_Sequence (gnat_node));
+      else
+	gnat_end_label = Empty;
+
       break;
 
     case N_Package_Declaration:
+      gcc_checking_assert (Present (Specification (gnat_node)));
       gnat_end_label = End_Label (Specification (gnat_node));
       break;