fix(sfc): component contains '<' only (#4753)

* fix(sfc): component contains '<' only

* update based on reviews

Author: dhcmrlchtdj

src/compiler/parser/html-parser.js

@@ -123,7 +123,7 @@ export function parseHTML (html, options) {
       }
 
       let text, rest, next
-      if (textEnd > 0) {
+      if (textEnd >= 0) {
         rest = html.slice(textEnd)
         while (
           !endTag.test(rest) &&

test/unit/modules/sfc/sfc-parser.spec.js

@@ -78,6 +78,15 @@ describe('Single File Component parser', () => {
     expect(res.template.content.trim()).toBe(`div\n  h1(v-if='1 < 2') hello`)
   })
 
+  it('should handle component contains "<" only', () => {
+    const res = parseComponent(`
+      <template>
+        <span><</span>
+      </template>
+    `)
+    expect(res.template.content.trim()).toBe(`<span><</span>`)
+  })
+
   it('should handle custom blocks without parsing them', () => {
     const res = parseComponent(`
       <template>