Opening attached project and "test" scene spawns "Mixer is not initialized" errors. When opening Audio Mixer window the errors below also appears:

The Master group is missing !!!
UnityEditor.DockArea:OnGUI()

NullReferenceException: Object reference not set to an instance of an object
UnityEditor.TreeViewDataSource.SetExpandedWithChildren (UnityEditor.TreeViewItem fromItem, Boolean expand) (at C:/buildslave/unity/build/Editor/Mono/GUI/TreeView/TreeViewDataSource.cs:198)
UnityEditor.AudioMixerGroupTreeView.LoadExpandedState () (at C:/buildslave/unity/build/Editor/Mono/Audio/Mixer/GUI/AudioMixerGroupTreeView.cs:630)
UnityEditor.AudioMixerGroupTreeView.OnMixerControllerChanged (UnityEditor.Audio.AudioMixerController controller) (at C:/buildslave/unity/build/Editor/Mono/Audio/Mixer/GUI/AudioMixerGroupTreeView.cs:603)
UnityEditor.AudioMixerWindow.OnMixerControllerChanged () (at C:/buildslave/unity/build/Editor/Mono/Audio/Mixer/GUI/AudioMixerWindow.cs:294)
UnityEditor.AudioMixerWindow.DetectControllerChange () (at C:/buildslave/unity/build/Editor/Mono/Audio/Mixer/GUI/AudioMixerWindow.cs:338)
UnityEditor.AudioMixerWindow.OnGUI () (at C:/buildslave/unity/build/Editor/Mono/Audio/Mixer/GUI/AudioMixerWindow.cs:418)
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono-runtime-and-classlibs/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:222)

ArgumentException: Getting control 0's position in a group with only 0 controls when doing Repaint
Aborting
UnityEngine.GUILayoutGroup.GetNext () (at C:/buildslave/unity/build/artifacts/EditorGenerated/GUILayoutUtility.cs:511)
UnityEngine.GUILayoutUtility.BeginLayoutGroup (UnityEngine.GUIStyle style, UnityEngine.GUILayoutOption[] options, System.Type LayoutType) (at C:/buildslave/unity/build/artifacts/EditorGenerated/GUILayoutUtility.cs:208)
UnityEditor.EditorGUILayout.BeginHorizontal (UnityEngine.GUIContent content, UnityEngine.GUIStyle style, UnityEngine.GUILayoutOption[] options) (at C:/buildslave/unity/build/Editor/Mono/EditorGUI.cs:5978)
UnityEditor.EditorGUILayout.BeginHorizontal (UnityEngine.GUIStyle style, UnityEngine.GUILayoutOption[] options) (at C:/buildslave/unity/build/Editor/Mono/EditorGUI.cs:5963)
UnityEditor.AudioMixerWindow.DoToolbar () (at C:/buildslave/unity/build/Editor/Mono/Audio/Mixer/GUI/AudioMixerWindow.cs:365)
UnityEditor.AudioMixerWindow.OnGUI () (at C:/buildslave/unity/build/Editor/Mono/Audio/Mixer/GUI/AudioMixerWindow.cs:424)
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono-runtime-and-classlibs/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:222)

TreeView root item is null. Ensure that your TreeViewDataSource sets up at least a root item.
UnityEditor.DockArea:OnGUI()

To reproduce:
- Simply open the attached project and observe "Mixer is not initialized" errors in Console
- Select the Audio Mixer named "AudioMixeræææææææææææææææææææææææøøøøøøøøøøøøøøøøøøøøøøøøøøøøøøøøøøøøøææææææææææææææææææææææææææøøøøøøøøøøøøøøøøøøøøøøøøøøøøææææææææææææææææææææææææææøfafsaasddfsdjhsklfh" or "NewAudioMixer"
- Observe the errors in Console

See also attached screen shots for details.