Prevent NPE

app/src/main/java/eu/faircode/email/FragmentRule.java

@@ -1146,9 +1146,11 @@ public class FragmentRule extends FragmentBase {
     private void onSelectSound(Uri uri) {
         try {
             Log.i("Selected sound uri=" + uri);
+            if (uri != null) {
                 getContext().getContentResolver().takePersistableUriPermission(uri, Intent.FLAG_GRANT_READ_URI_PERMISSION);
                 if (!Helper.isPersisted(getContext(), uri, true, false))
                     throw new IllegalStateException("No permission granted to access selected image " + uri);
+            }
         } catch (Throwable ex) {
             Log.w(ex);
         }