setShowcase method crash

[duz17]

setShowcase method use post delay without null check, causing this crash:

Fatal Exception: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.getLocationInWindow(int[])' on a null object reference
at com.github.amlcurran.showcaseview.targets.ViewTarget.getPoint(ViewTarget.java:41)
at com.github.amlcurran.showcaseview.ShowcaseView$1.run(ShowcaseView.java:191)
at android.os.Handler.handleCallback(Handler.java:761)
at android.os.Handler.dispatchMessage(Handler.java:98)
at android.os.Looper.loop(Looper.java:156)
at android.app.ActivityThread.main(ActivityThread.java:6523)
at java.lang.reflect.Method.invoke(Method.java)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:941)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:831)