Bug: Icons not showing when menu item is in a Dropdown

[sglebs]

Describe the bug

I have a menu entry which was at the root admin level but I moved it to inside a dropdown. Its icon no longer shows.

To Reproduce

• Create an AdminView with an icon at the root level, confirm it works
• Create a Dropdown, move the item above to inside the dropdown

Before:

    admin.add_view(KnowledgeIngestionProfileAdminView(model=KnowledgeIngestionProfile, icon="fa fa-file-import"))

After:

    admin.add_view(
        DropDown(
            "Knowledge Ingestion",
            icon="fa fa-list",
            views=[
                KnowledgeIngestionProfileAdminView(model=KnowledgeIngestionProfile, icon="fa fa-file-import", label="<<All>>"),
            ],
        )
    )

Environment (please complete the following information):

• Starlette-Admin version: 0.14.0
• ORM/ODMs: SQLAlchemy, psycopg2-binary==2.9.9
• SQLAlchemy-serializer==1.4.1

Additional context N/A

[sglebs]

Both active:

One with icon, the other one without.