Attempt to invoke virtual method 'void android.support.v7.widget.h.a()' on a null object reference

If the app is built with minifyEnabled true this error occur in the release build:

`02-05 14:59:23.136 14849-14849/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.wayzup.wayzupapp, PID: 14849
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.wayzup.wayzupapp/com.theartofdev.edmodo.cropper.CropImageActivity}: android.view.InflateException: Binary XML file line #37: Binary XML file line #37: Error inflating class android.support.v7.widget.Toolbar
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2946)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3046)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1688)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6809)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
Caused by: android.view.InflateException: Binary XML file line #37: Binary XML file line #37: Error inflating class android.support.v7.widget.Toolbar
Caused by: android.view.InflateException: Binary XML file line #37: Error inflating class android.support.v7.widget.Toolbar
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Constructor.newInstance0(Native Method)
at java.lang.reflect.Constructor.newInstance(Constructor.java:334)
at android.view.LayoutInflater.createView(LayoutInflater.java:647)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:790)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:730)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:863)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:824)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:866)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:824)
at android.view.LayoutInflater.inflate(LayoutInflater.java:515)
at android.view.LayoutInflater.inflate(LayoutInflater.java:423)
at android.view.LayoutInflater.inflate(LayoutInflater.java:374)
at android.support.v7.app.l.v(AppCompatDelegateImplV9.java:3406)
at android.support.v7.app.l.b(AppCompatDelegateImplV9.java:284)
at android.support.v7.app.d.setContentView(AppCompatActivity.java:139)
at com.theartofdev.edmodo.cropper.CropImageActivity.onCreate(CropImageActivity.java:58)
at android.app.Activity.performCreate(Activity.java:6998)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1230)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2899)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3046)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1688)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6809)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.h.a()' on a null object reference
at android.support.v7.widget.o.setBackgroundDrawable(AppCompatImageButton.java:123)
at android.view.View.setBackground(View.java:20428)
at android.view.View.(View.java:5226)
at android.widget.ImageView.(ImageView.java:176)
at android.widget.ImageButton.(ImageButton.java:86)
at android.widget.ImageButton.(ImageButton.java:82)
at android.support.v7.widget.o.(AppCompatImageButton.java:72)
at android.support.v7.widget.Toolbar.y(Toolbar.java:1361)
at android.support.v7.widget.Toolbar.c(Toolbar.java:917)
at android.support.v7.widget.Toolbar.(Toolbar.java:321)
at android.support.v7.widget.Toolbar.(Toolbar.java:228)`

I had this error in production, it does not occur in debug mode.

If I set minifyEnabled to false it will work

` buildTypes {
release {
minifyEnabled false
proguardFile 'proguard-android.txt'
zipAlignEnabled true
signingConfig signingConfigs.release
}
}`

It looks like we need a special config for proguard no ?