1、优化开启导航通道方法

lib/core/map_navigation_controller.dart

@@ -20,7 +20,7 @@ class MapNavigationController {
   }
 
   /// 开始定位
-  Future<void> startNav(Map startPoint, Map endPoint) {
+  Future<void> startNav(Map? startPoint, Map? endPoint) {
     return _methodChannel.startNav(startPoint, endPoint);
   }
 }

lib/core/map_navigation_method_channel.dart

@@ -66,7 +66,7 @@ class MethodChannelMapNavigation extends MapNavigationPlatform {
   }
 
   @override
-  Future<void> startNav(Map startPoint, Map endPoint) {
+  Future<void> startNav(Map? startPoint, Map? endPoint) {
     return channel().invokeMethod<void>('navigation#startNav', <String, dynamic>{
       'startPoint': startPoint,
       'endPoint': endPoint,