bwauth: use flag to do not warn when file is missing

Use flag to do not warn when the bandwidth file is missing trying
to serve it by http.
Also remove double space in the assignement.

src/feature/dircache/dircache.c

@@ -1451,7 +1451,8 @@ handle_get_next_bandwidth(dir_connection_t *conn,
   const or_options_t *options = get_options();
   if (options->V3BandwidthsFile) {
     int lifetime = 60;
-    char *bandwidth =  read_file_to_str(options->V3BandwidthsFile, 0, NULL);
+    char *bandwidth = read_file_to_str(options->V3BandwidthsFile,
+                                       RFTS_IGNORE_MISSING, NULL);
     size_t len = strlen(bandwidth);
     write_http_response_header(conn, len, NO_METHOD, lifetime);
     connection_buf_add(bandwidth, len, TO_CONN(conn));