fix scaffold appBar height without appBarBottom

example/lib/example_scaffold.dart

@@ -1,5 +1,6 @@
 import 'package:ansu_ui/ansu_ui.dart';
 import 'package:flutter/material.dart';
+import 'package:get/get.dart';
 
 class ExampleScaffold extends StatefulWidget {
   ExampleScaffold({Key key}) : super(key: key);
@@ -48,7 +49,18 @@ class _ExampleScaffoldState extends State<ExampleScaffold>
                 child: Text('open drawer'),
               );
             },
-          )
+          ),
+          TextButton(
+            onPressed: () {
+              Get.dialog(
+                ASScaffold(
+                  title: '框架 Scaffold',
+                ),
+                useSafeArea: false,
+              );
+            },
+            child: Text('open drawer'),
+          ),
         ],
       ),
     );

lib/scaffold/as_scaffold.dart

@@ -76,7 +76,11 @@ class _ASScaffoldState extends State<ASScaffold> {
                       ? Text(widget.title)
                       : widget.title ?? SizedBox(),
                 ),
-                bottom: widget.appBarBottom,
+                bottom: widget.appBarBottom ??
+                    PreferredSize(
+                      child: SizedBox(),
+                      preferredSize: Size.fromHeight(0),
+                    ),
               ),
       body: widget.body,
     );