Added an empty list return from parameter factories

Created by: stefanoborini

Small fix to return an empty list if the parameter_factories is undeclared. The default implementation should just return an empty list.

Created by: codecov[bot]

Codecov Report

Merging #157 into master will increase coverage by 0.65%. The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #157      +/-   ##
==========================================
+ Coverage   92.09%   92.74%   +0.65%     
==========================================
  Files          38       42       +4     
  Lines         999     1241     +242     
  Branches       66       90      +24     
==========================================
+ Hits          920     1151     +231     
- Misses         75       86      +11     
  Partials        4        4

Impacted Files	Coverage Δ
force_bdss/mco/base_mco_factory.py	100% <100%> (ø)
force_bdss/data_sources/i_data_source_factory.py	73.91% <0%> (-1.09%)
force_bdss/io/workflow_writer.py	100% <0%> (ø)
...orce_bdss/data_sources/base_data_source_factory.py	100% <0%> (ø)
force_bdss/ui_hooks/base_ui_hooks_factory.py	100% <0%> (ø)
...on_listeners/base_notification_listener_factory.py	100% <0%> (ø)
force_bdss/api.py	100% <0%> (ø)
..._bdss/mco/parameters/base_mco_parameter_factory.py	100% <0%> (ø)
force_bdss/core/base_factory.py	100% <0%> (ø)
... and 7 more

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Created by: stefanoborini

I can cover it, I just left it pending