Pasting formula content that created a formula group always constructed
group listeners, then destroyed those listeners again and reconstructed
the same listeners, because ScDocument::DeleteArea() is called with
IDF_OBJECTS again if nothing is excluded from paste. Do the listener
stuff only if one or more of the IDF_CONTENTS bits are set.

Change-Id: I8c6b7f7bb3402590f2b1f3259ee730f26a906cdf