BSA — method 'result()' of an AnalysisInstance object

Regarding method 'result()' of an AnalysisInstance object:
If a particular result does not exist (not yet, or at all), should
this method just ignore it, or to send back "an empty" Any (with tc kind
tc_void)?
Also we should specify what happen if methods result() and
get_result() are called when an analysis is in the states CREATED and/or
RUNNING (as we do it for TERMINATED* states).
Suggestion: it needs to be discuss whether some document clarification
would be enough, or if we want to have an additional exception.

accepted