input_filter.py throws a type error when filter type does not exist

[chipmuenk]

How to reproduce the issue:

• run python -m pyfda.input_widgets.input_filter
  (Lowpass, FIR, Equiripple should be selected)
• select 'Minimum Order'
• select 'Bandpass' ... and:

379: self.fo = foList[0] # use first list entry from filterTree

TypeError: 'dict_keys' object does not support indexing

Here, a minimum order bandpass is not contained in the filter dict. Consequently, it should not be selectable at all. But it is and it produces the error above.

[chipmuenk]

fixed in v0.1rc2