ve.ui.TextInputWidget: Fix TypeError when config is undefined

Parameter config is optional (both in the parent class and here),
this subclass forgot to add the fallback.

Though in a plain subclass the local fallback isn't needed
(parent class takes cares of it), in this case it is needed
since the constructor directly accesses config.multiline etc.

Change-Id: I3f9b73efb6c40a29efa221e1654b1247baaca281
Merge "ve.ui.TextInputWidget: Fix TypeError when config is undefined"