nothing more to do..?

i believe that the app is finished. ta-da!
Edit: actually ‘categories’ needs to be added

lib/pages/receipt_page.dart

@@ -75,8 +75,29 @@ class ReceiptPageState extends State<ReceiptPage> {
   void submitReceipt(String amount, String time, Organisation organisation) async {
     SystemChannels.textInput.invokeMethod('TextInput.hide');
 
-    if (demonstration)
-    {
+    if (amount == "" || time == "" || organisation == null) {
+      await showDialog(
+        context: context,
+        builder: (BuildContext context) {
+          // return object of type Dialog
+          return AlertDialog(
+            title: new Text("Invalid data"),
+            content: new Text(
+                "We couldn't process your request because one or more required fields are missing."),
+            actions: <Widget>[
+              new FlatButton(
+                child: new Text("OK"),
+                onPressed: () {
+                  Navigator.of(context).pop();
+                },
+              ),
+            ],
+          );
+        },
+      );
+    }
+    else {
+      if (demonstration) {
         await showDialog(
           context: context,
           builder: (BuildContext context) {
@@ -91,15 +112,14 @@ class ReceiptPageState extends State<ReceiptPage> {
                   onPressed: () {
                     Navigator.of(context).pop();
                     Navigator.of(context).pushReplacementNamed('/HomePage');
-                  //TODO: Reset form after dialog exit
                   },
                 ),
               ],
             );
           },
-      ).then((_) {
-    });
+        ).then((_) {});
       }
+
       else {
         Receipt receipt = new Receipt();
 
@@ -123,6 +143,7 @@ class ReceiptPageState extends State<ReceiptPage> {
         Navigator.of(context).pushReplacementNamed('/HomePage');
       }
     }
+  }
 
   String convertBoolToString(bool toConvert) {
     if (toConvert)