patch 8.2.3809: Vim9: crash when garbage collecting a nested partial

Problem:    Vim9: crash when garbage collecting a nested partial. (Virginia
            Senioria)
Solution:   Set references in all the funcstacks. (closes #9348)
diff --git a/src/eval.c b/src/eval.c
index abfde87..0a85b90 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -4510,6 +4510,9 @@
     // function call arguments, if v:testing is set.
     abort = abort || set_ref_in_func_args(copyID);
 
+    // funcstacks keep variables for closures
+    abort = abort || set_ref_in_funcstacks(copyID);
+
     // v: vars
     abort = abort || garbage_collect_vimvars(copyID);
 
@@ -4869,15 +4872,7 @@
 	    for (i = 0; i < pt->pt_argc; ++i)
 		abort = abort || set_ref_in_item(&pt->pt_argv[i], copyID,
 							ht_stack, list_stack);
-	    if (pt->pt_funcstack != NULL)
-	    {
-		typval_T    *stack = pt->pt_funcstack->fs_ga.ga_data;
-
-		for (i = 0; i < pt->pt_funcstack->fs_ga.ga_len; ++i)
-		    abort = abort || set_ref_in_item(stack + i, copyID,
-							 ht_stack, list_stack);
-	    }
-
+	    // pt_funcstack is handled in set_ref_in_funcstacks()
 	}
     }
 #ifdef FEAT_JOB_CHANNEL