Bug. UnboundLocalError while running the demos

[AhmadrezaHadi]

Hello,

While trying to execute the demos (following the tutorials) I noticed that I get the following error:
UnboundLocalError: local variable 'gripper_open' referenced before assignment
This error is originating from line#374 of scene.py. It will get fixed if you define the gripper_open variable inside the while or move line#344 outside the if statement.