[FIX] account_statement_base: Allow add lines from bank statment form view

TT50906

account_statement_base/models/account_bank_statement.py

@@ -4,6 +4,25 @@ from odoo import _, models
 class AccountBankStatement(models.Model):
     _inherit = "account.bank.statement"
 
+    # TODO: Delete if merged https://github.com/odoo/odoo/pull/182497
+    def _compute_date_index(self):
+        """The super() method does not take into account lines that do not have
+        internal_index set yet, and causes sorted() to fail, we need to re-define
+        the method in these cases to avoid the error.
+        """
+        _self = self
+        for stmt in self:
+            if any(not line.internal_index for line in stmt.line_ids):
+                _self -= stmt
+                sorted_lines = stmt.line_ids.filtered("internal_index").sorted(
+                    "internal_index"
+                )
+                stmt.first_line_index = sorted_lines[:1].internal_index
+                stmt.date = sorted_lines.filtered(lambda line: line.state == "posted")[
+                    -1:
+                ].date
+        return super(AccountBankStatement, _self)._compute_date_index()
+
     def action_open_statement_lines(self):
         self.ensure_one()
         if not self: