An Exception "Index out of bounds" have been thrown in business process

Failure
An Exception "Index out of bounds" have been thrown in business process designer after user tries to save implementation javascript via diagram properties.

Steps to reproduce:

1. Create new business process like shown in the attachment
2. There are 4 nodes and two connections
3. There are separately connected start with end event and two tasks
4. Select business rule task, go to diagram properties and add javascipt "alert("Hello work!")". Click "save"

Expected: An understandable error is shown
Actual: Exception "Index out of bounds" - for the first time and "Throwable" for all the next is shown