Fix recv_pkt_region incorrect usage

The `recv_pkt_region` is set when processing a flood packet in `filterRecvFloodPacket`
but direct/non-flood packets would never pass through that function, so the pointer was
not cleared for them.

`sendFloodReply` would then later use it blindly, which meant that the response would
either inherit the region from the last flood packet, or refer to a non-initialised pointer
if no region floods had been received yet.

examples/simple_room_server/MyMesh.cpp

@@ -290,8 +290,7 @@ bool MyMesh::allowPacketForward(const mesh::Packet *packet) {
   return true;
 }
 
-bool MyMesh::filterRecvFloodPacket(mesh::Packet* pkt) {
-  // just try to determine region for packet (apply later in allowPacketForward())
+mesh::DispatcherAction MyMesh::onRecvPacket(mesh::Packet* pkt) {
   if (pkt->getRouteType() == ROUTE_TYPE_TRANSPORT_FLOOD) {
     recv_pkt_region = region_map.findMatch(pkt, REGION_DENY_FLOOD);
   } else if (pkt->getRouteType() == ROUTE_TYPE_FLOOD) {
@@ -303,8 +302,7 @@ bool MyMesh::filterRecvFloodPacket(mesh::Packet* pkt) {
   } else {
     recv_pkt_region = NULL;
   }
-  // do normal processing
-  return false;
+  return Mesh::onRecvPacket(pkt);
 }
 
 void MyMesh::onAnonDataRecv(mesh::Packet *packet, const uint8_t *secret, const mesh::Identity &sender,
@@ -627,6 +625,7 @@ MyMesh::MyMesh(mesh::MainBoard &board, mesh::Radio &radio, mesh::MillisecondCloc
   _logging = false;
   region_load_active = false;
   set_radio_at = revert_radio_at = 0;
+  recv_pkt_region = NULL;
 
   // defaults
   memset(&_prefs, 0, sizeof(_prefs));