Do not create moves with a single empty line

issue9981
review343351002

CHANGELOG

@@ -1,3 +1,5 @@
+* Do not create moves with a single empty line
+
 Version 5.8.0 - 2020-11-02
 * Bug fixes (see mercurial logs for details)
 * Remove support for Python 3.5

stock.py

@@ -131,6 +131,9 @@ class Move(metaclass=PoolMeta):
         amount = Decimal('0.0')
         for line in account_move_lines:
             amount += line.debit - line.credit
+
+        if not amount:
+            return
         move_line = self._get_account_stock_move_line(amount)
         if move_line:
             account_move_lines.append(move_line)