```
type 'Null' is not a subtype of type 'Widget'
When the exception was thrown, this was the stack: 
#0      Home.build.<anonymous closure> (package:habittracker1/main.dart:230:29)
#1      SliverChildBuilderDelegate.build (package:flutter/src/widgets/sliver.dart:471:22)
#2      SliverMultiBoxAdaptorElement._build (package:flutter/src/widgets/sliver.dart:1236:28)
#3      SliverMultiBoxAdaptorElement.createChild.<anonymous closure> (package:flutter/src/widgets/sliver.dart:1250:55)
#4      BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2597:19)
#5      SliverMultiBoxAdaptorElement.createChild (package:flutter/src/widgets/sliver.dart:1242:12)
#6      RenderSliverMultiBoxAdaptor._createOrObtainChild.<anonymous closure> (package:flutter/src/rendering/sliver_multi_box_adaptor.dart:349:23)
#7      RenderObject.invokeLayoutCallback.<anonymous closure> (package:flutter/src/rendering/object.dart:2025:59)

```