Refactor dump_ct::cleanup_decl

To avoid repeatedly checking the same condition and so that `value` is
only in scope where it is required and non-empty.

Author: thomasspriggs

src/goto-instrument/dump_c.cpp

@@ -650,19 +650,15 @@ void dump_ct::cleanup_decl(
   std::list<irep_idt> &local_static,
   std::list<irep_idt> &local_type_decls)
 {
-  const optionalt<exprt> value = decl.initial_value();
+  goto_programt tmp;
+  tmp.add(goto_programt::make_decl(decl.symbol()));
 
-  if(value)
+  if(optionalt<exprt> value = decl.initial_value())
   {
     decl.set_initial_value({});
+    tmp.add(goto_programt::make_assignment(decl.symbol(), std::move(*value)));
   }
 
-  goto_programt tmp;
-  tmp.add(goto_programt::make_decl(decl.symbol()));
-
-  if(value)
-    tmp.add(goto_programt::make_assignment(decl.symbol(), *value));
-
   tmp.add(goto_programt::make_end_function());
 
   // goto_program2codet requires valid location numbers: