Android preview in Visual Studio for Mac

Hi guys,
I should use the preview for an Android device but I receive this error.

Creating class loader with 48 projects

Creating LibraryClassLoader in shadow copy path /var/folders/2g/dsdv9ryn5x7c39myn775z8pr0000gn/T/AndroidDesignerJars3034191262715436707
Setting id 2 on newly created ClassLoader

Trying to load class md5e940e1e778de0f856e343395a2f338c5.XFPageRendererView

mono.android.DesignerException: java.lang.NullPointerException
at mono.android.DesignerException.fromThrowable(DesignerException.java:46)
at mono.android.DesignerSession.checkRenderResultForError(DesignerSession.java:187)
at mono.android.DesignerSession.load(DesignerSession.java:239)
at mono.android.DesignerSession.processMessage(DesignerSession.java:702)
at mono.android.MessageListener.executeMessage(MessageListener.java:88)
at mono.android.MessageListener$Runner.run(MessageListener.java:44)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException
at android.os.storage.StorageManager.getVolumeList(StorageManager.java:922)
at android.os.Environment$UserEnvironment.getExternalDirs(Environment.java:87)
at android.os.Environment$UserEnvironment.buildExternalStoragePublicDirs(Environment.java:107)
at android.os.Environment.getExternalStoragePublicDirectory(Environment.java:588)
at md5b60ffeb829f638581ab2bb9b1a7f4f3f.PageRenderer.n_onAttachedToWindow(Native Method)
at md5b60ffeb829f638581ab2bb9b1a7f4f3f.PageRenderer.onAttachedToWindow(PageRenderer.java:55)
at android.view.View.dispatchAttachedToWindow(View.java:15395)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:2953)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:2960)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:2960)
at android.view.ViewGroup.dispatchAttachedToWindow(ViewGroup.java:2960)
at android.view.AttachInfo_Accessor.setAttachInfo(AttachInfo_Accessor.java:42)
at com.android.layoutlib.bridge.impl.RenderSessionImpl.inflate(RenderSessionImpl.java:333)
at com.android.layoutlib.bridge.Bridge.createSession(Bridge.java:429)
at com.android.ide.common.rendering.LayoutLibrary.createSession(LayoutLibrary.java:368)
at mono.android.DesignerSession.load(DesignerSession.java:233)
... 4 more