Error with String Item in Rules when string is Empty

[Josar]

@papabrenta

An error occured during the script execution: index=1, size=1
Seems to indicate that something OpenHAB expects was omitted :
like a matching bracket, a keyword, or a leading zero (like .05 instead of 0.05)

Maybe the above narrows what one is searching for to correct the error.

To help find missing brackets, paste offending rules into an editor such as Notepad++. When the cursor is near one bracket, such editors highlight what it sees as the matching bracket.

Please post the full rule. Maybe try to delete all other rules in the same file.