Or HaChaim on Genesis 18:29/אור החיים על בראשית י״ח:כ״ט

1 ויוסף עוד לדבר אליו. Abraham continued to speak to Him (G'd). This is a continuation of the prayer that G'd Himself should act as the one making up the requisite quorum. The expression ויוסף…אליו means that Abraham continued in the same vein adding that G'd's making up the quorum would apply even if not all the towns would could be saved by that method.