Handle deletion of contacts

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

@@ -1281,14 +1281,12 @@ class Core {
                 Log.i(folder.name + " updated id=" + message.id + " uid=" + message.uid + " unbrowse");
             }
 
-            if (message.avatar == null) {
             Uri lookupUri = ContactInfo.getLookupUri(context, message.from);
-                if (lookupUri != null) {
+            if ((message.avatar == null) == (lookupUri != null)) {
                 update = true;
-                    message.avatar = lookupUri.toString();
+                message.avatar = (lookupUri == null ? null : lookupUri.toString());
                 Log.i(folder.name + " updated id=" + message.id + " lookup=" + lookupUri);
             }
-            }
 
             if (update)
                 db.message().updateMessage(message);