CRM-13638 : verified and applied patch, just a minor modification done

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* CRM-13638: Saving an Activity record from Search causes "With Contact" field value to be deleted
  http://issues.civicrm.org/jira/browse/CRM-13638
Merge pull request #1849 from pratik-joshi/CRM-13638

CRM-13638 : verified and applied patch, just a minor modification done