validateVisitGroupField: if first child (not required) is absent 'Incorrect NumInGroup' error is raised
Created by: bl3ff
//start of repeating group
if int(fieldStack[0].tag) == fieldDef.Fields[0].Tag() {
childDefs = fieldDef.Fields
groupCount++
}
if fieldDef.Fields[0] is not a Required field could be not present in group,
but in this case groupCount would never be increment.