fix for commands not running from web interface context menu

[compso]

This is a fix for error when launching screening room from web context menu

ERROR: A general error was reported: invalid literal for int() with base 10: 'Screening'
Traceback (most recent call last):
File "/sgconf/SDG_dev/install/core/scripts/tank_cmd.py", line 1542, in 
cmd_line[1:])
File "/sgconf/SDG_dev/install/core/scripts/tank_cmd.py", line 501, in shotgun_run_action_auth
entity_ids = [int(x) for x in entity_ids_str]
ValueError: invalid literal for int() with base 10: 'Screening'