wcap-decode: Close file descriptor when destroying the decoder

wcap/wcap-decode.c

@@ -144,6 +144,7 @@ void
 wcap_decoder_destroy(struct wcap_decoder *decoder)
 {
 	munmap(decoder->map, decoder->size);
+	close(decoder->fd);
 	free(decoder->frame);
 	free(decoder);
 }