don't raise assertion failure

An reoccurring issue #5 and #8

qv.c

@@ -229,8 +229,13 @@ int yak_qv_solve(const int64_t *hist, const int64_t *cnt, int kmer, double fpr,
 	// compute adjusted qv
 	for (c = 0, adj_sum = 0.0; c < n_cnt; ++c)
 		adj_sum += qs->adj_cnt[c];
-	assert(adj_sum <= (double)qs->tot);
-	qs->err = qs->tot - adj_sum;
-	qs->qv = -4.3429448190325175 * log(log(qs->tot / adj_sum) / kmer);
+	if (adj_sum <= (double)qs->tot) {
+		qs->err = qs->tot - adj_sum;
+		qs->qv = -4.3429448190325175 * log(log(qs->tot / adj_sum) / kmer);
+	} else {
+		fprintf(stderr, "WARNING: failed to estimate the calibrated QV\n");
+		qs->err = 0;
+		qs->qv = qs->qv_raw;
+	}
 	return 0;
 }