Fileinput widget always returns None for name of uploaded file

[ltalirz]

As of panel 0.7.0 (with bokeh 1.4.0), the Fileinput widget does not set the name of the uploaded file.

E.g. in the following code

import panel as pn

inp = pn.widgets.FileInput(name='Upload')
btn = pn.widgets.Button(name='Upload', button_type='primary')
r= pn.Column(pn.Row(inp, btn),)

def on_click_parse(event):
    #print(inp.get_param_values())
    print(inp.filename)
btn.on_click(on_click_parse)

r.servable()

it always prints None to the terminal.

I can already see where the issue is and will open a PR.

[ltalirz]

Looking at the code from 0.6.2 that was reported to be working fine on SO, it seems to be unchanged in 0.7.
https://github.com/holoviz/panel/blob/v0.6.2/panel/widgets/input.py#L55

I.e. perhaps this was a change that crept in via a bokeh update?