Invocation of an activity with no return type in a conditional-test expression can cause an exception #22
Description
The invocation of an activity with no return type as the second or third operand of a conditional-test expression (which is legal per the Alf specification, with the invocation evaluating to null) results in a NullPointerException when the conditional-test expression is mapped. This is because the mapping for the invocation has no result source element in this case, but the mapping for the conditional-test expression expects the mappings for the second and third operands it to always have result source elements. (Note that similar cases are generally already handled correctly in other mappings.)