Adding a large number of invalid torrents causes GTK client to freeze

[Karl Richter]

Steps to reproduce:

1. run

   #!/usr/bin/python
   
   import os
   import tempfile
   import logging
   
   logger = logging.getLogger('deluge_issue')
   logger.setLevel(logging.INFO)
   logger_stdout_handler = logging.StreamHandler()
   logger_stdout_handler.setLevel(logging.INFO)
   logger_formatter = logging.Formatter('%(asctime)s:%(message)s')
   logger_stdout_handler.setFormatter(logger_formatter)
   logger.addHandler(logger_stdout_handler)
   
   def deluge_issue(file_count=1000):
       base_dir_path = tempfile.mkdtemp()
       logger.info("base directory path: %s" % (base_dir_path,))
       for i in range(file_count):
           file_name = os.path.join(base_dir_path, str(i)+".torrent")
           with open(file_name, 'a'):
               os.utime(file_name, None)
   
   if __name__ == "__main__":
       deluge_issue()
   

2. Open the dialog to add multiple torrents in deluge-gtk and select all torrents

The UI freezes and sometimes triggers a compiz bug which causes the whole desktop to freeze. I'm not expert enough to say if it's a deluge issue or of another program or library, but it'd be nice if you could investigate and give me extended feedback it's not a deluge issue so that I can report it at another location in case you don't want to do it.

experienced with deluge-gtk 2.0.0.dev7119+07a87fa+201711192317~ubuntu17.10.1 on Ubuntu 17.10