Fixed the logic in the __add_owner_s_equity method of the AccountCollector of the balance sheet, that when there is an existing balance, only set the URL when there's amount to be added.

src/accounting/report/reports/balance_sheet.py

@@ -235,9 +235,9 @@ class AccountCollector:
             = {x.account.code: x for x in self.accounts}
         if code in account_balance_by_code:
             balance: ReportAccount = account_balance_by_code[code]
-            balance.url = url
             if amount is not None:
                 balance.amount = balance.amount + amount
+                balance.url = url
             return
         # Add a new balance
         if amount is None: