Feedback Exception: >> Null check operator used on a null value <<

[calcitem]

Error:

Null check operator used on a null value

Stack trace:

#0 MaterialLocalizations.of (package:flutter/src/material/material_localizations.dart:516)
#1 _TextFieldState._getEffectiveDecoration (package:flutter/src/material/text_field.dart:903)
#2 _TextFieldState.build. (package:flutter/src/material/text_field.dart:1271)
#3 AnimatedBuilder.build (package:flutter/src/widgets/transitions.dart:1468)
#4 _AnimatedState.build (package:flutter/src/widgets/transitions.dart:174)
#5 StatefulElement.build (package:flutter/src/widgets/framework.dart:4691)
#6 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4574)
#7 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4746)
#8 Element.rebuild (package:flutter/src/widgets/framework.dart:4267)
#9 StatefulElement.update (package:flutter/src/widgets/framework.dart:4778)
#10 Element.updateChild (package:flutter/src/widgets/framework.dart:3350)
#11 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6090)
#12 Element.updateChild (package:flutter/src/widgets/framework.dart:3350)
#13 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4599)
#14 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4746)
#15 Element.rebuild (package:flutter/src/widgets/framework.dart:4267)
#16 StatefulElement.update (package:flutter/src/widgets/framework.dart:4778)
#17 Element.updateChild (package:flutter/src/widgets/framework.dart:3350)
#18 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4599)
#19 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4746)
#20 Element.rebuild (package:flutter/src/widgets/framework.dart:4267)
#21 StatefulElement.update (package:flutter/src/widgets/framework.dart:4778)
#22 Element.updateChild (package:flutter/src/widgets/framework.dart:3350)
#23 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6090)
#24 Element.updateChild (package:flutter/src/widgets/framework.dart:3350)
#25 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4599)
#26 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4746)
#27 Element.rebuild (package:flutter/src/widgets/framework.dart:4267)
#28 StatefulElement.update (package:flutter/src/widgets/framework.dart:4778)
#29 Element.updateChild (package:flutter/src/widgets/framework.dart:3350)
#30 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6090)
#31 Element.updateChild (package:flutter/src/widgets/framework.dart:3350)
#32 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6090)
#33 Element.updateChild (package:flutter/src/widgets/framework.dart:3350)
#34 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4599)
#35 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4746)
#36 Element.rebuild (package:flutter/src/widgets/framework.dart:4267)
#37 StatefulElement.update (package:flutter/src/widgets/framework.dart:4778)
#38 Element.updateChild (package:flutter/src/widgets/framework.dart:3350)
#39 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4599)
#40 StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4746)
#41 Element.rebuild (package:flutter/src/widgets/framework.dart:4267)
#42 StatefulElement.update (package:flutter/src/widgets/framework.dart:4778)
#43 Element.updateChild (package:flutter/src/widgets/framework.dart:3350)
#44 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6090)
#45 Element.updateChild (package:flutter/src/widgets/framework.dart:3350)
#46 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:6090)
#47 Element.updateChild (package:flutter/src/widgets/framework.dart:3350)
#48 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4599)
#49 Element.rebuild (package:flutter/src/widgets/framework.dart:4267)
#50 StatelessElement.update (package:flutter/src/widgets/framework.dart:4655)
#51 Element.updateChild (package:flutter/src/widgets/framework.dart:3350)
#52 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4599)