error

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.viztushar.urbanwalls/com.viztushar.urbanwalls.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.view.View.getPaddingLeft()' on a null object reference
                                                                              at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2659)
                                                                              at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2724)
                                                                              at android.app.ActivityThread.-wrap12(ActivityThread.java)
                                                                              at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1473)
                                                                              at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                              at android.os.Looper.loop(Looper.java:154)
                                                                              at android.app.ActivityThread.main(ActivityThread.java:6123)
                                                                              at java.lang.reflect.Method.invoke(Native Method)
                                                                              at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
                                                                              at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:757)
                                                                           Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.view.View.getPaddingLeft()' on a null object reference
                                                                              at com.mikepenz.materialdrawer.AccountHeaderBuilder.build(AccountHeaderBuilder.java:793)
                                                                              at com.viztushar.urbanwalls.MainActivity.onCreate(MainActivity.java:282)
                                                                              at android.app.Activity.performCreate(Activity.java:6672)
                                                                              at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1140)
                                                                              at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2612)
                                                                              at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2724) 
                                                                              at android.app.ActivityThread.-wrap12(ActivityThread.java) 
                                                                              at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1473) 
                                                                              at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                                              at android.os.Looper.loop(Looper.java:154) 
                                                                              at android.app.ActivityThread.main(ActivityThread.java:6123) 
                                                                              at java.lang.reflect.Method.invoke(Native Method) 
                                                                              at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867) 
                                                                              at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:757) 

header.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="178dp"
    android:background="@color/colorPrimary"
    android:orientation="vertical"
    android:weightSum="1">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:orientation="vertical">

        <TextView
            android:id="@+id/drawer_name"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="20dp"
            android:text="@string/app_name"
            android:textSize="18sp"
            android:textColor="#fff"
            android:textStyle="bold" />

    </LinearLayout>

    <ImageView
        android:id="@+id/drawer_icon"
        android:layout_width="64dp"
        android:layout_height="64dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="38dp"
        android:scaleType="centerCrop"
        android:src="@mipmap/ic_launcher"
        android:layout_marginStart="16dp" />
</RelativeLayout>