engine: Tweak conditions for enabling DLQ

Signed-off-by: Hiroshi Hatake <hiroshi@chronosphere.io>

Author: cosmo0920

src/flb_engine.c

@@ -245,7 +245,10 @@ static void handle_dlq_if_available(struct flb_config *config,
  struct flb_input_chunk *ic;
  struct cio_chunk *cio_ch;
 
- if (!config || !config->storage_keep_rejected || !task || !task->ic || !ins) {
+ if (!config ||
+ !config->storage_keep_rejected ||
+ !config->storage_path ||
+ !task || !task->ic || !ins) {
  return;
  }