AP_AHRS: add sanity checks for home location being set

libraries/AP_AHRS/AP_AHRS_DCM.cpp

@@ -1033,6 +1033,14 @@ bool AP_AHRS_DCM::airspeed_estimate(float *airspeed_ret) const
 
 bool AP_AHRS_DCM::set_home(const Location &loc)
 {
+    // check location is valid
+    if (loc.lat == 0 && loc.lng == 0 && loc.alt == 0) {
+        return false;
+    }
+    if (!check_latlng(loc)) {
+        return false;
+    }
+
     _home = loc;
     _home_is_set = true;