prevent crash due to Script __init__ exception

[w-e-w]

Description

a Script that for some reason fails to initialize can cause a webui to crash

for example a Script like this

from modules import scripts
class Script(scripts.Script):
    def __init__(self):
        assert False, 'This will crash webui'

this issue was brought to my attention by #14404
for whatever reason the this line in of code the extension triggers an uncaught exception and crashes web UI

Checklist:

• I have read contributing wiki page
• I have performed a self-review of my own code
• My code follows the style guidelines
• My code passes tests