AdminTagWidget remains collapsed after fieldset is opened

[StuartMacKay]

If you include a field that uses the AdminTagWidget in a fieldset where the initial state is collapsed, when the group is opened the field is zero width.

For example, the "topics" field:

    fieldsets = (None, {"fields": ("title", "summary", "tags", "publish",)},), (
        "Feed",
        {
            "classes": ("collapse",),
            "fields": (
                "author",
                "date",
                "topics",
            ),
        },
    )

When the "Feed" group is opened you see the following:

The field appears to be functional, you can click inside it and the dropdown appears - though it is zero-width also. Picking an item (presumably) does not change the width.

There is a formfield_overrides but it does not affect the behaviour:

    formfield_overrides = {
        models.CharField: {"widget": TextInput(attrs={"size": "80"})},
        models.URLField: {"widget": TextInput(attrs={"size": "80"})},
        TagField: {"widget": AdminTagWidget(attrs={"size": "80"})},
        models.TextField: {"widget": Textarea(attrs={"rows": "10", "cols": "80"})},
    }

Topic is a custom model but there is no additional media added:

from django.db import models
from django.utils.translation import gettext_lazy as _

import tagulous.models


class Topic(tagulous.models.TagTreeModel):
    class Meta:
        verbose_name = _("Topic")
        verbose_name_plural = _("Topics")

    class TagMeta:
        force_lowercase = True
        space_delimiter = False
        autocomplete_view = "topic_autocomplete"

    title = models.CharField(
        verbose_name=_("Title"),
        help_text=_("The human-readable name for the topic"),
        max_length=100,
        default="",
    )

    description = models.TextField(
        verbose_name=_("Description"),
        help_text=_("A short summary of what the topic covers"),
        blank=True,
    )

    def save(self, **kwargs):
        if not self.pk:
            self.title = self.name
        super().save(**kwargs)