Meshtastic crashes via an unimplemented routing module reply

Meshtastic is an open source mesh networking solution. From 1.2.1 until 2.6.2, a packet sent to the routing module that contains want_response==true causes a crash. This can lead to a degradation of service for nodes within range of a malicious sender, or via MQTT if downlink is enabled. This vulnerability is fixed in 2.6.2.