fix something more that gcc 15 doesn't like

Author: AllinCottrell

gui/gretl.c

@@ -821,7 +821,7 @@ int main (int argc, char **argv)
     fprintf(stderr, "finished option processing\n");
 #endif
 
-    /* set libgretl callbacks */
+    /* set libgretl callback functions */
     set_workdir_callback(gui_set_working_dir);
     set_show_activity_func(gui_show_activity);
     set_gui_model_list_callback(get_or_send_gui_models);

lib/src/objstack.c

@@ -1813,7 +1813,7 @@ int check_variable_deletion_list (int *list, const DATASET *dset)
 
 static GList *(*get_or_send_gui_models)(GList *);
 
-void set_gui_model_list_callback (GList *(*callback)())
+void set_gui_model_list_callback (GList *(*callback)(GList *))
 {
     get_or_send_gui_models = callback;
 }

lib/src/objstack.h

@@ -194,7 +194,7 @@ int check_models_for_subsample (char *newmask, int *ndropped);
 
 int n_stacked_models (void);
 
-void set_gui_model_list_callback (GList *(*callback)());
+void set_gui_model_list_callback (GList *(*callback)(GList *));
 
 void gretl_saved_objects_cleanup (void);