BottomBar crashes when "minSdkVersion" is set to 21

[Drakuwa]

Here's the stack trace from the Exception:

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.debug, PID: 24921
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.debug/com.example.activities.MainActivity}: android.view.InflateException: Binary XML file line #0: Binary XML file line #0: Error inflating class com.roughike.bottombar.BottomBar
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2762)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2848)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1552)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6334)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
Caused by: android.view.InflateException: Binary XML file line #0: Binary XML file line #0: Error inflating class com.roughike.bottombar.BottomBar
Caused by: android.view.InflateException: Binary XML file line #0: Error inflating class com.roughike.bottombar.BottomBar
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Constructor.newInstance0(Native Method)
at java.lang.reflect.Constructor.newInstance(Constructor.java:430)
at android.view.LayoutInflater.createView(LayoutInflater.java:645)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:787)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:727)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:858)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:821)
at android.view.LayoutInflater.inflate(LayoutInflater.java:518)
at android.view.LayoutInflater.inflate(LayoutInflater.java:426)
at android.view.LayoutInflater.inflate(LayoutInflater.java:377)
at android.support.v7.app.AppCompatDelegateImplV9.setContentView(AppCompatDelegateImplV9.java:287)
at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:139)
at com.example.activities.MainActivity.onCreate(MainActivity.kt:60)
at android.app.Activity.performCreate(Activity.java:6743)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1134)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2715)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2848)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1552)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6334)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
Caused by: java.lang.NoSuchFieldError: No field bb_bottom_bar_shadow of type I in class Lcom/roughike/bottombar/R$id; or its superclasses (declaration of 'com.roughike.bottombar.R$id' appears in /data/app/com.example.debug-1/base.apk)
at com.roughike.bottombar.BottomBar.initializeViews(BottomBar.java:270)
at com.roughike.bottombar.BottomBar.init(BottomBar.java:140)
at com.roughike.bottombar.BottomBar.(BottomBar.java:127)
at com.roughike.bottombar.BottomBar.(BottomBar.java:122)
at java.lang.reflect.Constructor.newInstance0(Native Method) 
at java.lang.reflect.Constructor.newInstance(Constructor.java:430) 
at android.view.LayoutInflater.createView(LayoutInflater.java:645) 
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:787) 
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:727) 
at android.view.LayoutInflater.rInflate(LayoutInflater.java:858) 
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:821) 
at android.view.LayoutInflater.inflate(LayoutInflater.java:518) 
at android.view.LayoutInflater.inflate(LayoutInflater.java:426) 
at android.view.LayoutInflater.inflate(LayoutInflater.java:377) 
at android.support.v7.app.AppCompatDelegateImplV9.setContentView(AppCompatDelegateImplV9.java:287) 
at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:139) 
at com.example.activities.MainActivity.onCreate(MainActivity.kt:60) // This is the setContentView(R.layout.activity_main) line from the onCreate() method
at android.app.Activity.performCreate(Activity.java:6743) 
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1134) 
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2715) 
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2848) 
at android.app.ActivityThread.-wrap12(ActivityThread.java) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1552) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:154) 
at android.app.ActivityThread.main(ActivityThread.java:6334) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

The crash doesn't happen when I set minSdkVersion 17

EDIT:
Since the bb_bottom_bar_shadow is mentioned in the stack trace as a "Cause", I tried removing the app:bb_showShadow="true" from the layout, which ended in the same crash.

Worth mentioning is that the layout I use only has the most basic width, height, alignParentBottom and bb_tabXmlResource attributes added and it lives in a RelativeLayout parent.

I'm using bottom-bar:2.3.1

[Drakuwa]

From what I can see here: https://github.com/roughike/BottomBar/blob/master/bottom-bar/src/main/java/com/roughike/bottombar/BottomBar.java#L270 shadowView is the only one not looking into rootView to find the desired View with given id (bb_bottom_bar_shadow), which could be the cause of the java.lang.NoSuchFieldError. Maybe the bb_bottom_bar_shadow id is present somewhere in a local layout (highly unlikely...)?