fix(#4917): suppress YAMLException when load js-yaml (#4927)

* it is just a workaround

Author: yoshinorin

lib/plugins/renderer/yaml.js

@@ -2,7 +2,19 @@
 
 const yaml = require('js-yaml');
 const { escape } = require('hexo-front-matter');
-const schema = yaml.DEFAULT_SCHEMA.extend(require('js-yaml-js-types').all);
+const log = require('hexo-log')();
+
+let schema = {};
+// FIXME: workaround for https://github.com/hexojs/hexo/issues/4917
+try {
+  schema = yaml.DEFAULT_SCHEMA.extend(require('js-yaml-js-types').all);
+} catch (e) {
+  if (e instanceof yaml.YAMLException) {
+    log.warn('YAMLException: please see https://github.com/hexojs/hexo/issues/4917');
+  } else {
+    throw e;
+  }
+}
 
 function yamlHelper(data) {
   return yaml.load(escape(data.text), { schema });