fix bug with trend

Author: CarGuo

lib/model/SearchUserQL.dart

@@ -26,7 +26,7 @@ class SearchUserQL {
       lang = map["lang"]["nodes"][0]["languages"]["nodes"][0]["name"];
     }
     return SearchUserQL(
-      followers: map["followers"]["totalCount"],
+      followers: map["followers"]?["totalCount"],
       name: map["name"],
       avatarUrl: map["avatarUrl"],
       bio: map["bio"],

lib/page/user/widget/user_item.dart

@@ -32,7 +32,7 @@ class UserItem extends StatelessWidget {
             placeholder: GSYICons.DEFAULT_USER_ICON,
             //预览图
             fit: BoxFit.fitWidth,
-            image: userItemViewModel.userPic!,
+            image: userItemViewModel.userPic ?? "https://github.com/CarGuo/gsy_github_app_flutter/blob/master/logo.png?raw=true",
             width: 40.0,
             height: 40.0,
           ),