T1856 FIX incoming emails when no reply-to is set

- The value could be empty but not false.

crm_request/models/request.py

@@ -162,7 +162,7 @@ def message_new(self, msg, custom_values=None):
             "categ_id": category_id,
             "name": subject,
             # Our contact forms use the reply-to field for the sponsor's email
-            "email_from": msg.get("reply_to", msg.get("from")),
+            "email_from": msg.get("reply_to") or msg.get("from", ""),
         }
 
         if "partner_id" not in custom_values: