Fix show models on dummy classifier/regressor

[franchuterivera]

Addresses this bug while printing a model:

AttributeError: 'MyDummyClassifier' object has no attribute 'dataset_properties'

[codecov]

Codecov Report

Merging #1114 (a808b61) into development (f518e9a) will increase coverage by 0.12%.
The diff coverage is 100.00%.

@@               Coverage Diff               @@
##           development    #1114      +/-   ##
===============================================
+ Coverage        85.46%   85.59%   +0.12%     
===============================================
  Files              137      137              
  Lines            10557    10563       +6     
===============================================
+ Hits              9023     9041      +18     
+ Misses            1534     1522      -12     

Impacted Files	Coverage Δ
autosklearn/evaluation/abstract_evaluator.py	90.03% <100.00%> (+1.01%)	⬆️
autosklearn/ensemble_builder.py	77.06% <0.00%> (+0.40%)	⬆️
...ature_preprocessing/select_rates_classification.py	87.32% <0.00%> (+1.40%)	⬆️
autosklearn/util/backend.py	76.15% <0.00%> (+1.42%)	⬆️
...eline/components/feature_preprocessing/fast_ica.py	97.82% <0.00%> (+6.52%)	⬆️

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[mfeurer]

While I think we should test for the dummy models complying with sklearn, we should not do so here. Could you please create a test in the evaluation module tests?