Fix to 2e672f3 decompress_peek_gz change.

The "zs.total_out < destsize" should have been "zs.avail_out" to be
more robust to total_out being reset by inflateReset.  However looking
again neither the avail_in or avail_out checks are necessary, as once
we hit the end of either input or output buffer the next cycle
triggers ret == Z_BUF_ERROR and we drop out as normal.

Thanks to John Marshall for the spot.

hts.c

@@ -328,19 +328,19 @@ decompress_peek_gz(hFILE *fp, unsigned char *dest, size_t destsize)
     unsigned char *last_in = buffer;
     while (zs.total_out < destsize) {
         ret = inflate(&zs, Z_SYNC_FLUSH);
-        if (ret == Z_STREAM_END && zs.avail_in && zs.total_out < destsize) {
+        if (ret == Z_STREAM_END) {
             if (last_in == zs.next_in)
-                break; // paranoia to avoid potential looping
+                break; // Paranoia to avoid potential looping. Shouldn't happen
             else
                 last_in = zs.next_in;
             inflateReset(&zs);
-            continue;
-        }
-        if (ret != Z_OK)
+        } else if (ret != Z_OK) {
+            // eg Z_BUF_ERROR due to avail_in/out becoming zero
             break;
+        }
     }
 
-    // zs.total_out can sometimes be wrong as inflateReset resets it
+    // NB: zs.total_out is changed by inflateReset, so use pointer diff instead
     destsize = zs.next_out - dest;
     inflateEnd(&zs);