fix: don't generate <title> tag if metaInfo.title is null or false (#409)

src/server/generators/title.js

@@ -8,6 +8,9 @@
 export default function titleGenerator (appId, { attribute } = {}, type, data) {
   return {
     text () {
+      if (!data) {
+        return ''
+      }
       return `<${type}>${data}</${type}>`
     }
   }

src/shared/escaping.js

@@ -1,4 +1,4 @@
-import { isString, isArray, isObject } from '../utils/is-type'
+import { isString, isArray, isPureObject } from '../utils/is-type'
 import { includes } from '../utils/array'
 import { metaInfoOptionKeys, disableOptionKeys } from './constants'
 
@@ -55,11 +55,11 @@ export function escape (info, options, escapeOptions) {
       escaped[key] = doEscape(value)
     } else if (isArray(value)) {
       escaped[key] = value.map((v) => {
-        return isObject(v)
+        return isPureObject(v)
           ? escape(v, options, escapeOptions)
           : doEscape(v)
       })
-    } else if (isObject(value)) {
+    } else if (isPureObject(value)) {
       escaped[key] = escape(value, options, escapeOptions)
     } else {
       escaped[key] = value

src/utils/is-type.js

@@ -15,6 +15,10 @@ export function isObject (arg) {
   return typeof arg === 'object'
 }
 
+export function isPureObject (arg) {
+  return typeof arg === 'object' && arg !== null
+}
+
 export function isFunction (arg) {
   return typeof arg === 'function'
 }