Allow removing avatars

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

@@ -202,6 +202,8 @@ public class EntityMessage implements Serializable {
     void getAvatar(Context context) {
         if (ContextCompat.checkSelfPermission(context, Manifest.permission.READ_CONTACTS)
                 == PackageManager.PERMISSION_GRANTED) {
+            this.avatar = null;
+
             try {
                 if (this.from != null)
                     for (int i = 0; i < this.from.length; i++) {

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

@@ -2167,11 +2167,10 @@ public class ServiceSynchronize extends LifecycleService {
                 Log.i(Helper.TAG, folder.name + " updated id=" + message.id + " uid=" + message.uid + " unhide");
             }
 
-            if (TextUtils.isEmpty(message.avatar)) {
-                message.getAvatar(context);
-                if (!TextUtils.isEmpty(message.avatar))
-                    update = true;
-            }
+            boolean noavatar = TextUtils.isEmpty(message.avatar);
+            message.getAvatar(context);
+            if (noavatar != TextUtils.isEmpty(message.avatar))
+                update = true;
 
             if (update)
                 db.message().updateMessage(message);