opencart/opencart — pull request #623 by Hrumpa (2013-04-16 07:20:36+00:00)
Title: Possible division by zero at Weight::convert()

When Weight_Format_ID ($from) is not set for the goods item record, method results with division by zero. Possibly the right idea is to output unchanged $value if either $this->weights[$from] OR $this->weights[$to] is not set.