Steps to reproduce:
1) Start a process instance with a business key '000258' (the process instance should contain a user task)
2) go to tasklist
3) search the task by Process Instance Business Key = 000258 (without single-quotes)

Problem:
The task is not found.
In order to query for the task the value of the query parameter "processInstanceBusinessKey" is parsed to an integer in tasklist. But in case of the business key it must be always a string.

Expected behavior:
The task is found

Hint:
In Cockpit I can query for the process instance by Process Instance Business Key = 000258 (without single-quotes) and the process instance is found.