Copy root lines as line when copying budget

Since b7a82bf780b4 the root lines field is no more copied and as lines are not
copied by default, we must copy the root lines as lines.

modules/account_budget/account.py

@@ -109,7 +109,7 @@ class BudgetMixin:
             default = {}
         else:
             default = default.copy()
-        default.setdefault('lines')
+        default.setdefault('lines', lambda data: data['root_lines'])
         return super().copy(budgets, default=default)
 
 
@@ -768,7 +768,7 @@ class CopyBudgetMixin:
         factor = self.start.factor
         if factor != 1:
             currency = self.start.company.currency
-            default['root_lines.amount'] = (
+            default['lines.amount'] = (
                 lambda data: currency.round(data['amount'] * factor)
                 if data['amount'] else data['amount'])
         return default