我想在表单中使imagefield为可选。我尝试了blank = True但它不起作用？

Question

我想在窗体中将imagefield设置为可选。为此，我给了blank = True null = True但它不起作用。堆栈溢出中有一些问题与我的问题有关，我尝试了所有答案但没有工作了吗？

 models.py
 class Profile(models.Model):
   user = models.OneToOneField(User,on_delete=models.CASCADE)
   image = models.ImageField(default='null',upload_to='pics',blank=True)

 view.py
 def register(request):
  if request.method == "POST":
    form = Register(request.POST,request.FILES)
    if form.is_valid():
        email = form.cleaned_data['Email']
        User_name=form.cleaned_data['Username']
        Password=form.cleaned_data['Password']
        firstname=form.cleaned_data['Firstname']
        lastname=form.cleaned_data['Lastname']
        user=User.objects.create_user(username=User_name,
                  password=Password,email=email,first_name=firstname,
                                                       last_name=lastname)
        insert = Profile(image = request.FILES('picture', None),user=user)
        return redirect('/')

  forms.py
  class Register(forms.Form):
      picture = forms.ImageField()  #i am posting only imagefield code