[Rspamd] Prevent LUA crash

Fixes LUA error when inserting unknown symbol from settings map

data/conf/rspamd/local.d/groups.conf

@@ -18,6 +18,9 @@ symbols {
   "ENCRYPTED_CHAT" {
     score = -20.0;
   }
+  "SOGO_CONTACT" {
+    score = -99.0;
+  }
 }
 
 group "MX" {