fixed app bar layout

lib/widgets/collection/app_bar.dart

@@ -155,7 +155,7 @@ class _CollectionAppBarState extends State<CollectionAppBar> with SingleTickerPr
       }
       return TappableAppBarTitle(
         onTap: _goToSearch,
-        title: title,
+        child: title,
       );
     } else if (collection.isSelecting) {
       return AnimatedBuilder(

lib/widgets/common/app_bar_title.dart

@@ -2,11 +2,11 @@ import 'package:flutter/material.dart';
 
 class TappableAppBarTitle extends StatelessWidget {
   final GestureTapCallback onTap;
-  final Widget title;
+  final Widget child;
 
   const TappableAppBarTitle({
     this.onTap,
-    @required this.title,
+    @required this.child,
   });
 
   @override
@@ -20,7 +20,7 @@ class TappableAppBarTitle extends StatelessWidget {
         padding: EdgeInsets.symmetric(horizontal: NavigationToolbar.kMiddleSpacing),
         color: Colors.transparent,
         height: kToolbarHeight,
-        child: title,
+        child: child,
       ),
     );
   }

lib/widgets/filter_grids/filter_grid_page.dart

@@ -42,13 +42,13 @@ class FilterNavigationPage extends StatelessWidget {
     return FilterGridPage(
       source: source,
       appBar: SliverAppBar(
-        title: SourceStateAwareAppBarTitle(
         title: TappableAppBarTitle(
           onTap: () => _goToSearch(context),
+          child: SourceStateAwareAppBarTitle(
             title: Text(title),
-          ),
             source: source,
           ),
+        ),
         actions: [
           SearchButton(source),
           ...(actions ?? []),