autotest: fix FenceMargin test

Author: andyp1per

Tools/autotest/arducopter.py

@@ -1929,7 +1929,8 @@ def FenceMargin(self, timeout=180):
         # 110m polyfence
         home_loc = self.mav.location()
         radius = self.get_parameter("FENCE_RADIUS")
-        self.mavproxy.send("map circle %f %f %f green\n" % (home_loc.lat, home_loc.lng, radius))
+        if self.use_map and self.mavproxy is not None:
+            self.mavproxy.send("map circle %f %f %f green\n" % (home_loc.lat, home_loc.lng, radius))
 
         locs = [
             self.offset_location_ne(home_loc, -110, -110),