Prevent m.relates_to to be removed from the status=1 object in encrypted rooms

lib/encryption/encryption.dart

@@ -267,6 +267,9 @@ class Encryption {
     if (sess == null) {
       throw ('Unable to create new outbound group session');
     }
+    // we clone the payload as we do not want to remove 'm.relates_to' from the
+    // original payload passed into this function
+    payload = Map<String, dynamic>.from(payload);
     final Map<String, dynamic> mRelatesTo = payload.remove('m.relates_to');
     final payloadContent = {
       'content': payload,