FileEnumertator::next_file() failed,why?

["chunlong84" <chunlong84 gmail com>]

	I use Gio::FileEnumerator to tranverse each file in a directory,but the call of FileEnumertator::next_file() failed during execution,why?
 
      Glib::RefPtr<Gio::File> file=Gio::File::create_for_path ("./data");
	  Glib::RefPtr<Gio::FileEnumerator> fileEnum=file->enumerate_children();
	  Glib::RefPtr<Gio::FileInfo> fileInfo;
	  while((fileInfo=fileEnum->next_file())!=NULL)       //failed
	  {
		  Glib::ustring filename="./data"+"/"+fileInfo->get_name();
		  Glib::ustring suffix=filename.substr(filename.size()-3,3);
		  if(suffix=="jpg" || suffix=="bmp" || suffix=="png")
			  filenameArray.push_back(filename);
	  }


   gdb result:

  glibmm-WARNING **: Failed to wrap object of type 'GLocalFileEnumerator'. Hint: this error is commonly caused by failing to    call a library init() function.    
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0xb6eda720 (LWP 13957)]
0xb761c2f4 in Gio::FileEnumerator::next_file () from /usr/lib/libgiomm-2.4.so.1