change some code

Author: CarGuo

lib/page/CodeDetailPage.dart

@@ -60,9 +60,7 @@ class _CodeDetailPageState extends State<CodeDetailPage> {
         if (res != null && res.result) {
           setState(() {
             data = res.data;
-            if (htmlUrl != null) {
-              titleOptionControl.url = htmlUrl;
-            }
+            titleOptionControl.url = htmlUrl ?? "";
           });
         }
       });

lib/page/LoginPage.dart

@@ -45,12 +45,8 @@ class _LoginPageState extends State<LoginPage> {
   initParams() async {
     _userName = await LocalStorage.get(Config.USER_NAME_KEY);
     _password = await LocalStorage.get(Config.PW_KEY);
-    if (_userName != null) {
-      userController.value = new TextEditingValue(text: _userName);
-    }
-    if (_password != null) {
-      pwController.value = new TextEditingValue(text: _password);
-    }
+    userController.value = new TextEditingValue(text: _userName ?? "");
+    pwController.value = new TextEditingValue(text: _password ?? "");
   }
 
   @override

lib/widget/HomeDrawer.dart

@@ -44,11 +44,11 @@ class HomeDrawer extends StatelessWidget {
               new UserAccountsDrawerHeader(
                 //Material内置控件
                 accountName: new Text(
-                  user.login != null ? user.login : "---",
+                  user.login ?? "---",
                   style: GSYConstant.largeTextWhite,
                 ),
                 accountEmail: new Text(
-                  user.email != null ? user.email : user.name != null ? user.name : "---",
+                  user.email ?? user.name ??  "---",
                   style: GSYConstant.subNormalText,
                 ),
                 //用户名
@@ -58,7 +58,7 @@ class HomeDrawer extends StatelessWidget {
                   onTap: () {},
                   child: new CircleAvatar(
                     //圆形图标控件
-                    backgroundImage: new NetworkImage(user.avatar_url != null ? user.avatar_url : "---"),
+                    backgroundImage: new NetworkImage(user.avatar_url ?? GSYICons.DEFAULT_REMOTE_PIC),
                   ),
                 ),
                 decoration: new BoxDecoration(