Fix internal assert on (obscure) side-effects in workflow

Remove redundant internal error.  I'm not sure why this line was there
since the following code was correct.  It could be triggered by an
expression with an implicit side-effect (e.g., a preceeding output)
used in a SEQUENTIAL which also happened to be dependent on some
other worflow actions.
(See example awrobel.eclxml in private regression suite.)

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>

ecl/hqlcpp/hqlttcpp.cpp

@@ -6178,7 +6178,6 @@ IHqlExpression * WorkflowTransformer::transformRootAction(IHqlExpression * expr)
     switch (op)
     {
     case no_compound:
-        throwUnexpected();
         if (expr->isAction())
             return createCompoundWorkflow(expr);
         break;