Fix the layout when there are no items.

lib/main.dart

@@ -118,11 +118,9 @@ class _HomePageState extends State<HomePage> {
             });
           },
         ),
-        body: Center(
-          child: Container(
+        body: Container(
           color: Theme.of(context).colorScheme.primaryContainer,
-            child: page,
-          ),
+          child: Center(child: page),
         ),
         floatingActionButton: floatingButton,
       );

lib/pages/expense.dart

@@ -12,7 +12,9 @@ class ExpensePage extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return ListView.builder(
+    return expenses.isEmpty
+        ? Text("Add expenses to get started!")
+        : ListView.builder(
             itemCount: expenses.length,
             itemBuilder: (_, index) {
               final Expense curr = expenses[index];