Icon not rendered for ui.stat

#### Wave SDK Version, OS
0.21.0 - tested locally OSK and also in the Editable Tour in Internal

#### Actual behavior
No waving blue hand next to 100 (grey hand to show this is a valid icon

#### Expected behavior

(A clear and concise description of what you expected to happen.)

#### Steps To Reproduce
```python
from h2o_wave import main, app, Q, ui

@app('/')
async def serve(q: Q):
q.page['example'] = ui.tall_stats_card(
box='1 1 2 4',
items=[
ui.stat(label='Fake', value='100', caption='test', icon='WavingHand', icon_color='blue'),
ui.stat(label='PARAMETER NAME', value='125%'),
ui.stat(label='PARAMETER NAME', value='578 Users'),
ui.stat(label='PARAMETER NAME', value='25K')
]
)
q.page["header"] = ui.header_card(
box="1 1 -1 1",
title="",
subtitle="",
icon="WavingHand"
)

await q.page.save()
```

Start by running the supplied Python reproduction with ui.tall_stats_card, ui.stat, and header_card on Wave 0.21.0, then compare how the WavingHand icon appears in each component. Done means the blue waving-hand icon renders next to the ui.stat value as it does for the header card.

Written by the indexing model from the issue text.