Allow keyguard_message_area_container to be null

In certain applications, the keyguard_message_area_container view may
not be present around a KeyguardMessageArea instance. Allowing the
container to be nullable and adding the appropriate null checks will
prevent exceptions under these circumstances.

Bug: 213476245
Test: manual
Change-Id: I65a4b6577c7b420ce6a55ae1d459989855c2e7a0

packages/SystemUI/src/com/android/keyguard/KeyguardMessageArea.java

@@ -30,6 +30,8 @@ import android.view.View;
 import android.view.ViewGroup;
 import android.widget.TextView;
 
+import androidx.annotation.Nullable;
+
 import com.android.internal.policy.SystemBarUtils;
 import com.android.settingslib.Utils;
 import com.android.systemui.R;
@@ -57,6 +59,11 @@ public class KeyguardMessageArea extends TextView implements SecurityMessageDisp
     private ColorStateList mNextMessageColorState = ColorStateList.valueOf(DEFAULT_COLOR);
     private boolean mBouncerVisible;
     private boolean mAltBouncerShowing;
+    /**
+     * Container that wraps the KeyguardMessageArea - may be null if current view hierarchy doesn't
+     * contain {@link R.id.keyguard_message_area_container}.
+     */
+    @Nullable
     private ViewGroup mContainer;
     private int mTopMargin;
 
@@ -75,6 +82,9 @@ public class KeyguardMessageArea extends TextView implements SecurityMessageDisp
     }
 
     void onConfigChanged() {
+        if (mContainer == null) {
+            return;
+        }
         final int newTopMargin = SystemBarUtils.getStatusBarHeight(getContext());
         if (mTopMargin == newTopMargin) {
             return;