Fix retrieve of digits for sum on list view

(transplanted from f0f94245cfb81b2c6e2baa8fa58602d264ff58bb)

tryton/gui/window/view_form/view/list_gtk/parser.py

@@ -189,10 +189,10 @@ class ParserTree(ParserInterface):
                         label.set_markup(label_str)
                     label_sum = gtk.Label()
                     label_sum.set_use_markup(True)
-                    if isinstance(fields.get('digits'), str):
+                    if isinstance(fields[fname].get('digits'), str):
                         digits = 2
                     else:
-                        digits = fields.get('digits', (16, 2))[1]
+                        digits = fields[fname].get('digits', (16, 2))[1]
                     dict_widget[i] = (fname, label, label_sum, digits,
                             label_bold)
             elif node.localName == 'button':