mdns: fixed crash on free undefined ptr after skipped strdup
mdns: fixed crash on free undefined ptr after skipped strdup

Shortcircuit evaluation may cause skip of _mdns_strdup_check of any further question field, which after clear_rx_packet freed undefined memory.
Fixes https://ezredmine.espressif.cn:8765/issues/28465

espressif/esp-idf,espressif/esp-idf,espressif/esp-idf,espressif/esp-idf