Shell script fails in v5

I have a rule I've been using for years, which files weblocs I create by dragging from browser address bar to desktop, creating a thumbnail along the way by means of a shell script. I've just run this manual workflow for the first time since upgrading to Catalina. The webloc file has stayed on the desktop and there's no thumbnail. I'm guessing this means the shell script is broken in Catalina? I'm a total noob as far as any kind of scripting. I'm hoping someone might be able to help me fix the script.
Screencap of the rule:
https://www.dropbox.com/s/cb9bgmx5kpw566a/screenshot_45.png?dl=0
Screencap of the shell script:
https://www.dropbox.com/s/yy3m4tw9xeh4o4x/screenshot_46.png?dl=0
Screencap of the rule:
https://www.dropbox.com/s/cb9bgmx5kpw566a/screenshot_45.png?dl=0
Screencap of the shell script:
https://www.dropbox.com/s/yy3m4tw9xeh4o4x/screenshot_46.png?dl=0