Don't crash trying to unregister a receiver twice.

Fixes: 190597198
Test: atest SystemUITests
Change-Id: I04c8cca24f9823bab5244126052d31d1b3549c5f

packages/SystemUI/src/com/android/systemui/volume/SafetyWarningDialog.java

@@ -101,7 +101,12 @@ abstract public class SafetyWarningDialog extends SystemUIDialog
 
     @Override
     public void onDismiss(DialogInterface unused) {
-        mContext.unregisterReceiver(mReceiver);
+        try {
+            mContext.unregisterReceiver(mReceiver);
+        } catch (IllegalArgumentException e) {
+            // Don't crash if the receiver has already been unregistered.
+            e.printStackTrace();
+        }
         cleanUp();
     }