rs6000: fix symtab_node::get == NULL issue

	PR target/102349

gcc/ChangeLog:

	* config/rs6000/rs6000.c (rs6000_xcoff_encode_section_info):
	Check that we have a symbol summary for a symbol.

gcc/config/rs6000/rs6000.c

@@ -21728,6 +21728,7 @@ rs6000_xcoff_encode_section_info (tree decl, rtx rtl, int first)
   if (decl
       && DECL_P (decl)
       && VAR_OR_FUNCTION_DECL_P (decl)
+      && symtab_node::get (decl) != NULL
       && symtab_node::get (decl)->alias == 0
       && symname[strlen (symname) - 1] != ']')
     {