fix missing type in argument parser

bin/aln2taxaffi.py

@@ -74,7 +74,7 @@ def parse_arguments():
     parser.add_argument('-c', '--min_coverage', default=70,
                         help="percentage of coverage")
 
-    parser.add_argument('--top', default=10,
+    parser.add_argument('--top', default=10, type=int,
                         help="Keep diamond alignments within this percentage range of top alignment score")
 
     parser.add_argument('--keep_only_best_aln',