[FIX] account: statement line reconciliation cancel

Cancelling a statement line should not remove the
according journal items if they are associated
to an `account.payment`.

In this case, this should simply remove
the `statement_id` of the move lines,
and unmark the `account.payment` as
reconciled.

opw-674896

addons/account/models/account_bank_statement.py

@@ -419,17 +419,21 @@ class AccountBankStatementLine(models.Model):
 
     @api.multi
     def button_cancel_reconciliation(self):
-        # TOCKECK : might not behave as expected in case of reconciliations (match statement line with already
-        # registered payment) or partial reconciliations : it will completely remove the existing payment.
-        move_recs = self.env['account.move']
+        moves_to_unbind = self.env['account.move']
+        moves_to_cancel = self.env['account.move']
         for st_line in self:
-            move_recs = (move_recs | st_line.journal_entry_ids)
-        if move_recs:
-            for move in move_recs:
+            moves_to_unbind |= st_line.journal_entry_ids
+            for move in st_line.journal_entry_ids:
+                if any(line.payment_id for line in move.line_ids):
+                    continue
+                moves_to_cancel |= st_line.journal_entry_ids
+        if moves_to_unbind:
+            moves_to_unbind.write({'statement_line_id': False})
+        if moves_to_cancel:
+            for move in moves_to_cancel:
                 move.line_ids.remove_move_reconcile()
-            move_recs.write({'statement_line_id': False})
-            move_recs.button_cancel()
-            move_recs.unlink()
+            moves_to_cancel.button_cancel()
+            moves_to_cancel.unlink()
 
     ####################################################
     # Reconciliation interface methods