Clear username and password field on failed login

src/components/login_form/login_form.js

@@ -10,7 +10,11 @@ const LoginForm = {
     submit () {
       this.$store.dispatch('loginUser', this.user).then(
         () => { this.$router.push('/main/friends')}, 
-        () => { this.authError = true }
+        () => {
+          this.authError = true
+          this.user.username = ''
+          this.user.password = ''
+        }
       )
     }
   }