[Fix] Do not break history on NaN in required score

Issue: #763
Reported by: @fatalbanana

src/controller.c

@@ -1277,9 +1277,17 @@ rspamd_controller_handle_history (struct rspamd_http_connection_entry *conn_ent,
 					row->action)), "action", 0, false);
 			ucl_object_insert_key (obj, ucl_object_fromdouble (
 					row->score),		  "score",			0, false);
-			ucl_object_insert_key (obj,
-				ucl_object_fromdouble (
-					row->required_score), "required_score", 0, false);
+
+			if (!isnan (row->required_score)) {
+				ucl_object_insert_key (obj,
+						ucl_object_fromdouble (
+								row->required_score), "required_score", 0, false);
+			}
+			else {
+				ucl_object_insert_key (obj,
+						ucl_object_fromdouble (0.0), "required_score", 0, false);
+			}
+
 			ucl_object_insert_key (obj, ucl_object_fromstring (
 					row->symbols),		  "symbols",		0, false);
 			ucl_object_insert_key (obj,	   ucl_object_fromint (