bug fix: get_all_synonyms could return undef instead of empty list

modules/Bio/EnsEMBL/DBEntry.pm

@@ -63,7 +63,7 @@ sub new_fast {
   my $class = shift;
   my $hashref = shift;
   bless $hashref, $class;
-  $hashref->{_synonyms} = [];
+  $hashref->{synonyms} = [];
   
   return $hashref;
 }