Fix #434 - return correct bStatus

[mattroumaya]

Overview

Fix #434

• Check that workflow exists in lAssessments before running assessment.
• If workflow is missing, alert with cli and return bStatus == FALSE

Test Notes/Sample Code

 custom_assessments <- MakeAssessmentList()
 custom_assessments$ie$workflow <- NULL
 result <- Study_Assess(lAssessments = custom_assessments)

Confirm result$ie$bStatus == FALSE

[samussiah]

Noice.