Fix auto crash report (for non GPS devices trying to do follow me)

java.lang.IllegalArgumentException: requested provider gps doesn't exisit
at android.os.Parcel.readException(Parcel.java:1429)
at android.os.Parcel.readException(Parcel.java:1379)
at android.location.ILocationManager$Stub$Proxy.requestLocationUpdates(ILocationManager.java:646)
at android.location.LocationManager._requestLocationUpdates(LocationManager.java:660)
at android.location.LocationManager.requestLocationUpdates(LocationManager.java:482)
at com.geeksville.andropilot.service.FollowMe$$anon$1.<init>(FollowMe.scala:40)
at com.geeksville.andropilot.service.FollowMe.<init>(FollowMe.scala:38)
at com.geeksville.andropilot.service.AndropilotService.setFollowMe(AndropilotService.scala:241)
at com.geeksville.andropilot.gui.MainActivity.onOptionsItemSelected(MainActivity.scala:466)
at android.app.Activity.onMenuItemSelected(Activity.java:2534)
at android.support.v4.app.FragmentActivity.onMenuItemSelected(FragmentActivity.java:361)
at com.android.internal.policy.impl.PhoneWindow.onMenuItemSelected(PhoneWindow.java:958)
at com.android.internal.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:735)
at com.android.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:149)
at com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:874)
at com.android.internal.view.menu.MenuPopupHelper.onItemClick(MenuPopupHelper.java:156)
at android.widget.AdapterView.performItemClick(AdapterView.java:298)
at android.widget.AbsListView.performItemClick(AbsListView.java:1086)
at android.widget.AbsListView$PerformClick.run(AbsListView.java:2855)
at android.widget.AbsListView$1.run(AbsListView.java:3529)
at android.os.Handler.handleCallback(Handler.java:615)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4745)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method
1.0.06 - only ask for waypoints after we see waypoint_current