Check desired vs. actual behaviour if both target feature and annotation type parms are missing

[johann-petrak]

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Re-check what the intended behaviour is when combinations of the optional parameters are missing.

There seems to be a bug in the EvaluateClassification PR when both classAnnotationType and targetFeature are missing: this PR is supposed to also support sequence tagging (unlike the classification PR).
At least in cases when it is really a classification problem, leaving the two parameters empty throws an array out of bounds exception rather than showing some reasonable error message.