Add unexpected-null-character' error.

Author: inikulin

.gitignore

@@ -1,4 +1,5 @@
 .idea
+.vscode
 node_modules
 docs/build
 docs/05_api_reference.md

lib/common/error_codes.js

@@ -5,5 +5,6 @@ module.exports = {
     nonUnicodeCharacterInInputStream: 'non-unicode-character-in-input-stream',
     selfClosingNonVoidHtmlElement: 'self-closing-non-void-html-element',
     endTagWithAttributes: 'end-tag-with-attributes',
-    selfClosingEndTag: 'self-closing-end-tag'
+    selfClosingEndTag: 'self-closing-end-tag',
+    unexpectedNullCharacter: 'unexpected-null-character'
 };

lib/tokenizer/index.js

@@ -644,8 +644,10 @@ _[DATA_STATE] = function dataState(cp) {
     else if (cp === $.LESS_THAN_SIGN)
         this.state = TAG_OPEN_STATE;
 
-    else if (cp === $.NULL)
+    else if (cp === $.NULL) {
+        this._err(ERR.unexpectedNullCharacter, null);
         this._emitCodePoint(cp);
+    }
 
     else if (cp === $.EOF)
         this._emitEOFToken();