java.lang.RuntimeException: Failed to call observer method

[YasserMuhamed2017]

Could anyone here to help how to solve this exception ?

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.android.trackmysleepquality, PID: 4117
java.lang.RuntimeException: Failed to call observer method
at androidx.lifecycle.ClassesInfoCache$MethodReference.invokeCallback(ClassesInfoCache.java:226)
at androidx.lifecycle.ClassesInfoCache$CallbackInfo.invokeMethodsForEvent(ClassesInfoCache.java:194)
at androidx.lifecycle.ClassesInfoCache$CallbackInfo.invokeCallbacks(ClassesInfoCache.java:185)
at androidx.lifecycle.ReflectiveGenericLifecycleObserver.onStateChanged(ReflectiveGenericLifecycleObserver.java:37)
at androidx.lifecycle.LifecycleRegistry$ObserverWithState.dispatchEvent(LifecycleRegistry.java:361)
at androidx.lifecycle.LifecycleRegistry.forwardPass(LifecycleRegistry.java:300)
at androidx.lifecycle.LifecycleRegistry.sync(LifecycleRegistry.java:339)
at androidx.lifecycle.LifecycleRegistry.moveToState(LifecycleRegistry.java:145)
at androidx.lifecycle.LifecycleRegistry.handleLifecycleEvent(LifecycleRegistry.java:131)
at androidx.fragment.app.Fragment.performStart(Fragment.java:2735)
at androidx.fragment.app.FragmentStateManager.start(FragmentStateManager.java:355)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1192)
at androidx.fragment.app.FragmentManager.addAddedFragments(FragmentManager.java:2222)
at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:1995)
at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1951)
at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:1847)
at androidx.fragment.app.FragmentManager$4.run(FragmentManager.java:413)
at android.os.Handler.handleCallback(Handler.java:873)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:201)
at android.app.ActivityThread.main(ActivityThread.java:6810)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:873)
Caused by: java.lang.IllegalArgumentException: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull, parameter item
at com.example.android.trackmysleepquality.sleeptracker.BindingUtilsKt.setSleepImage(Unknown Source:7)
at com.example.android.trackmysleepquality.databinding.FragmentSleepDetailBindingImpl.executeBindings(FragmentSleepDetailBindingImpl.java:145)
at androidx.databinding.ViewDataBinding.executeBindingsInternal(ViewDataBinding.java:473)
at androidx.databinding.ViewDataBinding.executePendingBindings(ViewDataBinding.java:445)
at androidx.databinding.ViewDataBinding$OnStartListener.onStart(ViewDataBinding.java:1687)
at java.lang.reflect.Method.invoke(Native Method)
at androidx.lifecycle.ClassesInfoCache$MethodReference.invokeCallback(ClassesInfoCache.java:216)
at androidx.lifecycle.ClassesInfoCache$CallbackInfo.invokeMethodsForEvent(ClassesInfoCache.java:194) 
at androidx.lifecycle.ClassesInfoCache$CallbackInfo.invokeCallbacks(ClassesInfoCache.java:185) 
at androidx.lifecycle.ReflectiveGenericLifecycleObserver.onStateChanged(ReflectiveGenericLifecycleObserver.java:37) 
at androidx.lifecycle.LifecycleRegistry$ObserverWithState.dispatchEvent(LifecycleRegistry.java:361) 
at androidx.lifecycle.LifecycleRegistry.forwardPass(LifecycleRegistry.java:300) 
at androidx.lifecycle.LifecycleRegistry.sync(LifecycleRegistry.java:339) 
at androidx.lifecycle.LifecycleRegistry.moveToState(LifecycleRegistry.java:145) 
at androidx.lifecycle.LifecycleRegistry.handleLifecycleEvent(LifecycleRegistry.java:131) 
at androidx.fragment.app.Fragment.performStart(Fragment.java:2735) 
at androidx.fragment.app.FragmentStateManager.start(FragmentStateManager.java:355) 
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1192) 
at androidx.fragment.app.FragmentManager.addAddedFragments(FragmentManager.java:2222) 
at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:1995) 
at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1951) 
at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:1847) 
at androidx.fragment.app.FragmentManager$4.run(FragmentManager.java:413) 
at android.os.Handler.handleCallback(Handler.java:873) 
at android.os.Handler.dispatchMessage(Handler.java:99) 
at android.os.Looper.loop(Looper.java:201) 
at android.app.ActivityThread.main(ActivityThread.java:6810) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:873)