Show outline icon when no new messages

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

@@ -68,6 +68,9 @@ public class Widget extends AppWidgetProvider {
 
                     views.setOnClickPendingIntent(R.id.widget, pi);
 
+                    views.setImageViewResource(R.id.ivMessage, unseen == 0
+                            ? R.drawable.baseline_mail_outline_24
+                            : R.drawable.baseline_mail_24);
                     views.setTextViewText(R.id.tvCount, unseen < 100 ? nf.format(unseen) : "∞");
 
                     if (!TextUtils.isEmpty(name)) {

app/src/main/res/layout/widget.xml

@@ -8,6 +8,7 @@
     android:padding="6dp">
 
     <ImageView
+        android:id="@+id/ivMessage"
         android:layout_width="24dp"
         android:layout_height="0dp"
         android:layout_gravity="center_horizontal"