Don't error when making an iterator on a tid not in the index

hts.c

@@ -3077,16 +3077,14 @@ hts_itr_t *hts_itr_query(const hts_idx_t *idx, int tid, hts_pos_t beg, hts_pos_t
                 free(iter);
                 iter = NULL;
             }
+        } else if (tid >= idx->n || (bidx = idx->bidx[tid]) == NULL) {
+            iter->finished = 1;
         } else {
             if (beg < 0) beg = 0;
             if (end < beg) {
               free(iter);
               return NULL;
             }
-            if (tid >= idx->n || (bidx = idx->bidx[tid]) == NULL) {
-              free(iter);
-              return NULL;
-            }
 
             k = kh_get(bin, bidx, META_BIN(idx));
             if (k != kh_end(bidx))

test/modhdr.expected.vcf

@@ -0,0 +1,4 @@
+##fileformat=VCFv4.3
+##FILTER=<ID=PASS,Description="All filters passed">
+##contig=<ID=chr22,length=51304566>
+#CHROM	POS	ID	REF	ALT	QUAL	FILTER	INFO

test/test.pl

@@ -947,6 +947,11 @@ sub test_vcf_various
         cmd => "$$opts{bin}/htsfile -c $$opts{path}/formatmissing.vcf");
     test_cmd($opts, %args, out => "vcf_meta_meta.vcf",
         cmd => "$$opts{bin}/htsfile -c $$opts{path}/vcf_meta_meta.vcf");
+
+    # VCF file with contig IDX=1, simulating an edited BCF file
+    # See htslib issue 1534
+    test_cmd($opts, %args, out => "modhdr.expected.vcf",
+        cmd => "$$opts{path}/test_view $$opts{path}/modhdr.vcf.gz chr22:1-2");
 }
 
 sub write_multiblock_bgzf {

test/test_view.c

@@ -224,7 +224,8 @@ int vcf_loop(int argc, char **argv, int optind, struct opts *opts, htsFile *in,
             hts_itr_t *iter;
             if ((iter = bcf_itr_querys(idx, h, argv[i])) == 0) {
                 fprintf(stderr, "[E::%s] fail to parse region '%s'\n", __func__, argv[i]);
-                continue;
+                exit_code = 1;
+                break;
             }
             while ((r = bcf_itr_next(in, iter, b)) >= 0) {
                 if (!opts->benchmark && bcf_write1(out, h, b) < 0) {