Gateway Widget - Table Size Change Fix

Fix gateway widget size change on first update.

Inner table size changes on the first update because the table in update data does not have the same attributes as the widget.  i.e. border, cellpadding, cellspacing,  style & summary.

Also remove an errant td end tag.


Populate gateway address field with tilde if there is no address or friendly interface.
This is to match the update data.
I still think this block would look better if it does something like:
```
$if_gw = ''
if ($gateway['ipprotocol'] == "inet")
	$if_gw = htmlspecialchars(get_interface_gateway($gateway['friendlyiface']));
else if ($gateway['ipprotocol'] == "inet6")
	$if_gw = htmlspecialchars(get_interface_gateway_v6($gateway['friendlyiface']));

echo ($if_gw = '' ? '~' : $if_gw);
unset($if_gw);
```
It avoids calling the same functions multiple times