frip now checks for empty files

frips = []

for idx, bam_file in enumerate(bam_file_list):

    # Init

    frip = 0

    # Read first line

    first_line = None

    with open(peak_file_list[idx], "r") as file:

        for line in file:

            first_line = line

            break

    if first_line is not None:

        print("Calculating " + bam_file + " using " + peak_file_list[idx])

        cr = crpb.CountReadsPerBin([bam_file], bedFile=[peak_file_list[idx]], numberOfProcessors=int(args.threads))

        # Calc frip

        frip = float(total[0]) / bam.mapped

    frips.append(str(frip))

    # Log