EXCEPTION CAUGHT BY WIDGETS LIBRARY

[gameorised]

I/flutter (18452): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter (18452): The following NoSuchMethodError was thrown building Expanded(flex: 1):
I/flutter (18452): The method '>=' was called on null.
I/flutter (18452): Receiver: null
I/flutter (18452): Tried calling: >=(0.0)
I/flutter (18452): The relevant error-causing widget was:
I/flutter (18452): Expanded
I/flutter (18452): file:///C:/src/flutter/flutter/.pub-cache/hosted/pub.dartlang.org/firebase_ui-1.0.8/lib/flutter_firebase_ui.dart:69:23
I/flutter (18452): When the exception was thrown, this was the stack:
I/flutter (18452): #0 Object.noSuchMethod (dart:core-patch/object_patch.dart:53:5)
I/flutter (18452): #1 EdgeInsetsGeometry.isNonNegative (package:flutter/src/painting/edge_insets.dart:51:18)
I/flutter (18452): #2 new RenderPadding (package:flutter/src/rendering/shifted_box.dart:107:23)
I/flutter (18452): #3 Padding.createRenderObject (package:flutter/src/widgets/basic.dart:1630:12)
I/flutter (18452): #4 RenderObjectElement.mount (package:flutter/src/widgets/framework.dart:5366:28)
I/flutter (18452): #5 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:5829:11)
I/flutter (18452): ... Normal element mounting (7 frames)
I/flutter (18452): #12 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3446:14)
I/flutter (18452): #13 MultiChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:5947:32)
I/flutter (18452): ... Normal element mounting (34 frames)
I/flutter (18452): #47 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3446:14)
I/flutter (18452): #48 MultiChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:5947:32)
I/flutter (18452): ... Normal element mounting (201 frames)
I/flutter (18452): #249 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3446:14)
I/flutter (18452): #250 MultiChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:5947:32)
I/flutter (18452): ... Normal element mounting (253 frames)
I/flutter (18452): #503 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3446:14)
I/flutter (18452): #504 Element.updateChild (package:flutter/src/widgets/framework.dart:3214:18)
I/flutter (18452): #505 RenderObjectToWidgetElement._rebuild (package:flutter/src/widgets/binding.dart:1148:16)
I/flutter (18452): #506 RenderObjectToWidgetElement.mount (package:flutter/src/widgets/binding.dart:1119:5)
I/flutter (18452): #507 RenderObjectToWidgetAdapter.attachToRenderTree. (package:flutter/src/widgets/binding.dart:1061:17)
I/flutter (18452): #508 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2607:19)
I/flutter (18452): #509 RenderObjectToWidgetAdapter.attachToRenderTree (package:flutter/src/widgets/binding.dart:1060:13)
I/flutter (18452): #510 WidgetsBinding.attachRootWidget (package:flutter/src/widgets/binding.dart:941:7)
I/flutter (18452): #511 WidgetsBinding.scheduleAttachRootWidget. (package:flutter/src/widgets/binding.dart:922:7)
I/flutter (18452): (elided 11 frames from class _RawReceivePortImpl, class _Timer, dart:async, and dart:async-patch)
I/flutter (18452): ════════════════════════════════════════════════════════════════════════════════════════════════════

════════ Exception caught by widgets library ═══════════════════════════════════════════════════════
The following NoSuchMethodError was thrown building Expanded(flex: 1):
The method '>=' was called on null.
Receiver: null
Tried calling: >=(0.0)

The relevant error-causing widget was:
SignInScreen file:///C:/Users/MAHFOOZ-PC/Desktop/firebaseui1/lib/main.dart:68:18
When the exception was thrown, this was the stack:
#0 Object.noSuchMethod (dart:core-patch/object_patch.dart:53:5)
#1 EdgeInsetsGeometry.isNonNegative (package:flutter/src/painting/edge_insets.dart:51:18)
#2 new RenderPadding (package:flutter/src/rendering/shifted_box.dart:107:23)
#3 Padding.createRenderObject (package:flutter/src/widgets/basic.dart:1630:12)
#4 RenderObjectElement.mount (package:flutter/src/widgets/framework.dart:5366:28)
...
════════════════════════════════════════════════════════════════════════════════════════════════════
D/dalvikvm(18452): threadid=15: thread exiting, not yet detached (count=0)
Lost connection to device.