ublox_msg.cc: simplify map operations in gen_nav_data (#2004)

* simplify map operations in gen_nav_data

* same as before

* rebase master

selfdrive/locationd/ublox_msg.cc

@@ -282,13 +282,15 @@ kj::Array<capnp::word> UbloxMsgParser::gen_nav_data() {
     for(int i = 0; i < msg->numWords;i++)
       words.push_back(measurements[i].dwrd);
 
-    if(subframeId == 1) {
-      nav_frame_buffer[msg->gnssId][msg->svid] = subframes_map();
-      nav_frame_buffer[msg->gnssId][msg->svid][subframeId] = words;
-    } else if(nav_frame_buffer[msg->gnssId][msg->svid].find(subframeId-1) != nav_frame_buffer[msg->gnssId][msg->svid].end())
-      nav_frame_buffer[msg->gnssId][msg->svid][subframeId] = words;
-    if(nav_frame_buffer[msg->gnssId][msg->svid].size() == 5) {
-      EphemerisData ephem_data(msg->svid, nav_frame_buffer[msg->gnssId][msg->svid]);
+    subframes_map &map = nav_frame_buffer[msg->gnssId][msg->svid];
+    if (subframeId == 1) {
+      map = subframes_map();
+      map[subframeId] = words;
+    } else if (map.find(subframeId-1) != map.end()) {
+      map[subframeId] = words;
+    }
+    if(map.size() == 5) {
+      EphemerisData ephem_data(msg->svid, map);
       MessageBuilder msg_builder;
       auto eph = msg_builder.initEvent().initUbloxGnss().initEphemeris();
       eph.setSvId(ephem_data.svId);