use proper constructor for code_expressiont

Author: Daniel Kroening

src/goto-programs/remove_function_pointers.cpp

@@ -420,9 +420,8 @@ void remove_function_pointerst::remove_function_pointer(
 
   // We preserve the original dereferencing to possibly catch
   // further pointer-related errors.
-  code_expressiont code_expression;
+  code_expressiont code_expression(function);
   code_expression.add_source_location()=function.source_location();
-  code_expression.expression()=function;
   target->code.swap(code_expression);
   target->type=OTHER;