CRM-14367 - don't white screen when no pdfs

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* CRM-14367: Add ability to group contribution letters by contact (& possibly recurring contribution)
  http://issues.civicrm.org/jira/browse/CRM-14367
CRM-14367 - always apply aggregates

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* CRM-14367: Add ability to group contribution letters by contact (& possibly recurring contribution)
  http://issues.civicrm.org/jira/browse/CRM-14367
assign aggregrates for grouped & non-grouped as no real performance hit & more predictable