qt new_channel_dialog: fix regression: oepn chan with "max" amt
qt new_channel_dialog: fix regression: oepn chan with "max" amt

```
E | gui.qt.exception_window.Exception_Hook | exception caught by crash reporter
Traceback (most recent call last):
  File "...\electrum\electrum\gui\qt\channels_list.py", line 377, in new_channel_with_warning
	self.new_channel_dialog()
  File "...\electrum\electrum\gui\qt\channels_list.py", line 399, in new_channel_dialog
	return d.run()
  File "...\electrum\electrum\gui\qt\new_channel_dialog.py", line 133, in run
	if self.min_amount_sat and funding_sat < self.min_amount_sat:
TypeError: '<' not supported between instances of 'str' and 'int'
```

pooler/electrum-ltc,spesmilo/electrum,pooler/electrum-ltc,pooler/electrum-ltc,spesmilo/electrum,spesmilo/electrum,spesmilo/electrum,pooler/electrum-ltc