fix(compiler): update v-if directive to use Comment instead of Empty (#208)

packages/compiler-core/src/codegen.ts

@@ -211,6 +211,9 @@ export function generate(
         // to provide the helper here.
         if (ast.hoists.length) {
           push(`const _${helperNameMap[CREATE_VNODE]} = Vue.createVNode\n`)
+          if (ast.helpers.includes(COMMENT)) {
+            push(`const _${helperNameMap[COMMENT]} = Vue.Comment\n`)
+          }
         }
       }
     }
@@ -484,7 +487,7 @@ function genComment(node: CommentNode, context: CodegenContext) {
   if (__DEV__) {
     const { push, helper } = context
     push(
-      `${helper(CREATE_VNODE)}(${helper(COMMENT)}, 0, ${JSON.stringify(
+      `${helper(CREATE_VNODE)}(${helper(COMMENT)}, null, ${JSON.stringify(
         node.content
       )})`,
       node