What happened when Tom gave his account of the night in the graveyard? Is he worried about the murderer? Why or why not?

Finally, the sleepy town of St. Petersburg begins to stir again as the trial for the murder of Dr. Robinson begins. Since witnessing the murder, neither Huck nor Tom has divulged the events of that night to anyone for fear of Injun Joe's wrath. But by and by, the two boys recall Muff Potter's ­ falsely accused of the murder ­ good nature: how he had mended their kites, tied their fishing lines, and "stood by [Huck] when [he] was out of luck."