运行结果及报错内容 file4=as.character(paste(aa,"/",aa,"-",Fre,"-gene",".txt", sep="")) x <- read.dna(file4, format = "fasta") h <- haplotype(x)Error in as.matrix.DNAbin(x) : DNA sequences in list not of the same length.出现这样的情况应该如何解决呢？