Null check operator used on a null value for carousel controller [dev]

[f1sh1918]

Describe the bug
There is an scheduler library expression in the console if the app was startet and the carousel controller was not ready

To Reproduce
Steps to reproduce the behavior:

1. Start the app.
2. Check the run task of your simulator/emulator

======== Exception caught by scheduler library =====================================================
The following _TypeError was thrown during a scheduler callback:
Null check operator used on a null value

When the exception was thrown, this was the stack: 
#0      CarouselControllerImpl.jumpToPage (package:carousel_slider/carousel_controller.dart:92:38)
#1      IdentificationPageState.initState.<anonymous closure> (package:ehrenamtskarte/identification/identification_page.dart:40:26)
#2      SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1386:15)
#3      SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1322:11)
#4      SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:1169:5)
#5      _invoke (dart:ui/hooks.dart:312:13)
#6      PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:399:5)
#7      _drawFrame (dart:ui/hooks.dart:283:31)
====================================================================================================

Expected behavior
It will be waited until the controller is ready, before trying to jump to a particular card index