adding javascript "this.disabled" invalidate ManyToManyField

[liwee]

With just models.py and admin.py, I was able to save a poll without any problems.
But if you add onClick="this.disabled=true; this.form.submit()", even if you try to add qn to the poll, it will not get saved

submit_line.html

{% if show_save_and_continue %}<input onClick="this.disabled=true; this.form.submit();" type="submit" value="{% trans 'Save and continue editing' %}" name="_continue" />{% endif %}

models.py

from django.db import models

class Question(models.Model):
    qn = models.CharField(max_length=200)

    def __unicode__(self):
        return self.qn
			
class Poll(models.Model):
    name = models.CharField(max_length=200)
    qn = models.ManyToManyField(Question)

admin.py

from django.contrib import admin
from .models import *

class PollAdmin(admin.ModelAdmin):
	filter_horizontal = ('qn',)

admin.site.register(Poll, PollAdmin)
admin.site.register(Question)