try to import an empty group - get this error:

PHP notice Trying to get property of non-object

sites/limesurvey-205beta/application/helpers/admin/import_helper.php(875)

863 $aGIDReplacements[$oldgid]=$newgid; // add old and new qid to the mapping array
864 }
865 }
866
867
868 // Import questions table ===================================================================================
869
870 // We have to run the question table data two times - first to find all main questions
871 // then for subquestions (because we need to determine the new qids for the main questions first)
872
873
874 $results['questions']=0;
875 foreach ($xml->questions->rows->row as

If no question is in the file it causes this error...

foreach ($xml->questions->rows->row as this is the problem!

A solution

Should be if ($xml->questions){foreach ($xml->questions->rows->row}