Camera Deactivates when integrating GVR in Vuforia

I'm trying to integrate Google Cardboard SDK to Vuforia Unity project. The way of achieving this is described here. My problem is that the camera gets deactivated when in Play mode along with this big Error:

 Exception in callback: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.ArgumentException: An element with the same key already exists in the dictionary.
   at System.Collections.Generic.Dictionary`2[UnityEngine.Camera,Vuforia.VideoBackgroundAbstractBehaviour].Add (UnityEngine.Camera key, Vuforia.VideoBackgroundAbstractBehaviour value) [0x0007e] in /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Collections.Generic/Dictionary.cs:404 
   at Vuforia.BaseStereoViewerCameraConfiguration.ResolveVideoBackgroundBehaviours () [0x00000] in <filename unknown>:0 
   at Vuforia.BaseCameraConfiguration.Init () [0x00000] in <filename unknown>:0 
   at Vuforia.DigitalEyewearARController.ConfigureView () [0x00000] in <filename unknown>:0 
   at Vuforia.DigitalEyewearARController.OnVuforiaStarted () [0x00000] in <filename unknown>:0 
   at (wrapper managed-to-native) System.Reflection.MonoMethod:InternalInvoke (object,object[],System.Exception&)
   at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x000d0] in /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:222 
   --- End of inner exception stack trace ---
   at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x000eb] in /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:232 
   at System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) [0x00000] in /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MethodBase.cs:115 
   at System.Delegate.DynamicInvokeImpl (System.Object[] args) [0x000b9] in /Users/builduser/buildslave/mono/build/mcs/class/corlib/System/Delegate.cs:443 
   at System.MulticastDelegate.DynamicInvokeImpl (System.Object[] args) [0x00018] in /Users/builduser/buildslave/mono/build/mcs/class/corlib/System/MulticastDelegate.cs:71 
   at System.Delegate.DynamicInvoke (System.Object[] args) [0x00000] in /Users/builduser/buildslave/mono/build/mcs/class/corlib/System/Delegate.cs:415 
   at Vuforia.DelegateHelper.InvokeDelegate (System.Delegate action, System.Object[] args) [0x00000] in <filename unknown>:0 
 UnityEngine.Debug:LogError(Object)
 Vuforia.DelegateHelper:InvokeDelegate(Delegate, Object[])
 Vuforia.DelegateHelper:InvokeWithExceptionHandling(Action)
 Vuforia.VuforiaARController:Start()
 System.Delegate:DynamicInvoke(Object[])
 Vuforia.DelegateHelper:InvokeDelegate(Delegate, Object[])
 Vuforia.DelegateHelper:InvokeWithExceptionHandling(Action)
 Vuforia.VuforiaAbstractBehaviour:Start()

I am using Unity 5.6.03f and Vuforia 0.6.2