it show its not null safety

[HDEVCODER]

Launching lib/main.dart on iPhone 12 in debug mode...
Xcode build done. 26.3s
Failed to build iOS app
Error output from Xcode build:
↳
objc[66174]: Class AppleTypeCRetimerRestoreInfoHelper is implemented in both /usr/lib/libauthinstall.dylib (0x203305eb0) and /Library/Apple/System/Library/PrivateFrameworks/MobileDevice.framework/Versions/A/MobileDevice (0x105dc44f8). One of the two will be used. Which one is undefined.
objc[66174]: Class AppleTypeCRetimerFirmwareAggregateRequestCreator is implemented in both /usr/lib/libauthinstall.dylib (0x203305f00) and /Library/Apple/System/Library/PrivateFrameworks/MobileDevice.framework/Versions/A/MobileDevice (0x105dc4548). One of the two will be used. Which one is undefined.
objc[66174]: Class AppleTypeCRetimerFirmwareRequestCreator is implemented in both /usr/lib/libauthinstall.dylib (0x203305f50) and /Library/Apple/System/Library/PrivateFrameworks/MobileDevice.framework/Versions/A/MobileDevice (0x105dc4598). One of the two will be used. Which one is undefined.
objc[66174]: Class ATCRTRestoreInfoFTABFile is implemented in both /usr/lib/libauthinstall.dylib (0x203305fa0) and /Library/Apple/System/Library/PrivateFrameworks/MobileDevice.framework/Versions/A/MobileDevice (0x105dc45e8). One of the two will be used. Which one is undefined.
objc[66174]: Class AppleTypeCRetimerFirmwareCopier is implemented in both /usr/lib/libauthinstall.dylib (0x203305ff0) and /Library/Apple/System/Library/PrivateFrameworks/MobileDevice.framework/Versions/A/MobileDevice (0x105dc4638). One of the two will be used. Which one is undefined.
objc[66174]: Class ATCRTRestoreInfoFTABSubfile is implemented in both /usr/lib/libauthinstall.dylib (0x203306040) and /Library/Apple/System/Library/PrivateFrameworks/MobileDevice.framework/Versions/A/MobileDevice (0x105dc4688). One of the two will be used. Which one is undefined.
2022-06-09 18:48:27.884 xcodebuild[66174:4886075] Requested but did not find extension point with identifier Xcode.IDEKit.ExtensionSentinelHostApplications for extension Xcode.DebuggerFoundation.AppExtensionHosts.watchOS of plug-in com.apple.dt.IDEWatchSupportCore
2022-06-09 18:48:27.884 xcodebuild[66174:4886075] Requested but did not find extension point with identifier Xcode.IDEKit.ExtensionPointIdentifierToBundleIdentifier for extension Xcode.DebuggerFoundation.AppExtensionToBundleIdentifierMap.watchOS of plug-in com.apple.dt.IDEWatchSupportCore
** BUILD FAILED **
Xcode's output:
↳
Writing result bundle at path:
/var/folders/6w/1vyh848s2cn7l1dcqvl82_xc0000gn/T/flutter_tools.ncZySy/flutter_ios_build_temp_dirVf1CMt/temporary_xcresult_bundle
: Error: Method 'addPostFrameCallback' cannot be called on 'SchedulerBinding?' because it is potentially null.

• 'SchedulerBinding' is from 'package:flutter/src/scheduler/binding.dart' ('../../../../../development/flutter/packages/flutter/lib/src/scheduler/binding.dart').
  Try calling using ?. instead.
  SchedulerBinding.instance.addPostFrameCallback((_) {
  ^^^^^^^^^^^^^^^^^^^^
  : Error: Method 'addPostFrameCallback' cannot be called on 'SchedulerBinding?' because it is potentially null.
• 'SchedulerBinding' is from 'package:flutter/src/scheduler/binding.dart' ('../../../../../development/flutter/packages/flutter/lib/src/scheduler/binding.dart').
  Try calling using ?. instead.
  SchedulerBinding.instance.addPostFrameCallback((_) {
  ^^^^^^^^^^^^^^^^^^^^
  Failed to package /Users/abdulrahmansalimalhamodi/Desktop/Flutter/apps/beta/hotellna.
  Command PhaseScriptExecution failed with a nonzero exit code
  note: Using new build system
  note: Planning
  note: Build preparation complete
  note: Building targets in dependency order
  /Users/abdulrahmansalimalhamodi/Desktop/Flutter/apps/beta/hotellna/ios/Pods/Pods.xcodeproj: warning: The iOS Simulator deployment target 'IPHONEOS_DEPLOYMENT_TARGET' is set to 8.0, but the range of supported deployment target versions is 9.0 to 15.4.99. (in target 'BoringSSL-GRPC' from project 'Pods')
  /Users/abdulrahmansalimalhamodi/Desktop/Flutter/apps/beta/hotellna/ios/Pods/Pods.xcodeproj: warning: The iOS Simulator deployment target 'IPHONEOS_DEPLOYMENT_TARGET' is set to 8.0, but the range of supported deployment target versions is 9.0 to 15.4.99. (in target 'abseil' from project 'Pods')
  /Users/abdulrahmansalimalhamodi/Desktop/Flutter/apps/beta/hotellna/ios/Pods/Pods.xcodeproj: warning: The iOS Simulator deployment target 'IPHONEOS_DEPLOYMENT_TARGET' is set to 8.0, but the range of supported deployment target versions is 9.0 to 15.4.99. (in target 'gRPC-Core' from project 'Pods')
  /Users/abdulrahmansalimalhamodi/Desktop/Flutter/apps/beta/hotellna/ios/Pods/Pods.xcodeproj: warning: The iOS Simulator deployment target 'IPHONEOS_DEPLOYMENT_TARGET' is set to 8.0, but the range of supported deployment target versions is 9.0 to 15.4.99. (in target 'gRPC-C++' from project 'Pods')
  /Users/abdulrahmansalimalhamodi/Desktop/Flutter/apps/beta/hotellna/ios/Pods/Pods.xcodeproj: warning: The iOS Simulator deployment target 'IPHONEOS_DEPLOYMENT_TARGET' is set to 8.0, but the range of supported deployment target versions is 9.0 to 15.4.99. (in target 'leveldb-library' from project 'Pods')
  /Users/abdulrahmansalimalhamodi/Desktop/Flutter/apps/beta/hotellna/ios/Pods/Pods.xcodeproj: warning: The iOS Simulator deployment target 'IPHONEOS_DEPLOYMENT_TARGET' is set to 8.0, but the range of supported deployment target versions is 9.0 to 15.4.99. (in target 'gRPC-C++-gRPCCertificates-Cpp' from project 'Pods')
  Result bundle written to path:
  /var/folders/6w/1vyh848s2cn7l1dcqvl82_xc0000gn/T/flutter_tools.ncZySy/flutter_ios_build_temp_dirVf1CMt/temporary_xcresult_bundle
  Could not build the application for the simulator.
  Error launching application on iPhone 12.
  Exited (sigterm)

[Sayuru99]

main.dart line 53

onSubmit: (val) {
          print(val);
        },