use gtk_tree_view_get_n_columns

instead of g_list_length (gtk_tree_view_get_columns (tree))

gnucash/gnome-utils/gnc-tree-view.c

@@ -2154,13 +2154,7 @@ gint
 gnc_tree_view_append_column (GncTreeView *view,
                              GtkTreeViewColumn *column)
 {
-    GList *columns;
-    int n;
-
-    /* There's no easy way to get this number. */
-    columns = gtk_tree_view_get_columns (GTK_TREE_VIEW(view));
-    n = g_list_length (columns);
-    g_list_free (columns);
+    int n = gtk_tree_view_get_n_columns (GTK_TREE_VIEW(view));
 
     /* Ignore the initial column, the selection menu */
     if (n >= 1)
@@ -2177,7 +2171,7 @@ get_column_next_to (GtkTreeView *tv, GtkTreeViewColumn **col, gboolean backward)
     gboolean wrapped = FALSE;
 
     cols = gtk_tree_view_get_columns (tv);
-    g_return_val_if_fail (g_list_length (cols) > 0, FALSE);
+    g_return_val_if_fail (cols != NULL, FALSE);
 
     node = g_list_find (cols, *col);
     g_return_val_if_fail (node, FALSE);

gnucash/import-export/csv-imp/assistant-csv-price-import.cpp

@@ -1646,9 +1646,7 @@ void CsvImpPriceAssist::preview_refresh_table ()
 
     /* Start with counting the current number of columns (ntcols)
      * we have in the treeview */
-    auto columns = gtk_tree_view_get_columns (treeview);
-    auto ntcols = g_list_length(columns);
-    g_list_free (columns);
+    auto ntcols = gtk_tree_view_get_n_columns (treeview);
 
     /* Drop redundant columns if the model has less data columns than the new model
      * ntcols = n° of columns in treeview (1 error column + x data columns)

gnucash/import-export/csv-imp/assistant-csv-trans-import.cpp

@@ -1572,9 +1572,7 @@ void CsvImpTransAssist::preview_refresh_table ()
 
     /* Start with counting the current number of columns (ntcols)
      * we have in the treeview */
-    auto columns = gtk_tree_view_get_columns (treeview);
-    auto ntcols = g_list_length(columns);
-    g_list_free (columns);
+    auto ntcols = gtk_tree_view_get_n_columns (treeview);
 
     /* Drop redundant columns if the model has less data columns than the new model
      * ntcols = n° of columns in treeview (1 error column + x data columns)