tuned: clarified old_theory (in contrast to 4d5342898b1);

--- a/src/Pure/PIDE/headless.scala	Sun Oct 16 13:10:47 2022 +0200
+++ b/src/Pure/PIDE/headless.scala	Sun Oct 16 13:18:54 2022 +0200
@@ -613,8 +613,9 @@
           for (theory <- loaded_theories)
           yield {
             val node_name = theory.node_name
+            val old_theory = st.theories.get(node_name)
             val theory1 = theory.set_required(st1.is_required(node_name))
-            val edits = theory1.node_edits(st1.theories.get(node_name))
+            val edits = theory1.node_edits(old_theory)
             (edits, (node_name, theory1))
           }
         val file_edits =