WebComment: deleted record message

• When trying to display comments from a deleted record, inform the user that the record has been deleted instead of replying that the record does not exist (in '/comments' tab) or displaying no output ('yourcomments' page).

Signed-off-by: Jerome Caffaro <jerome.caffaro@cern.ch>
Tested-by: Tibor Simko <tibor.simko@cern.ch>