StringIndexOutOfBoundsException with empty sort string

[MichaelVonB]

Steps to reproduce

• camunda-bpm-taskpool version: 3.16.0
• Camunda BPM version: x
• JDK version: 17
• Steps: (what exactly are you doing with the above reproducer?) When providing polyflow with an empty sort string ("") for example in TasksWithDataEntriesForUserQuery I get an StringIndexOutOfBoundsException

Expected behaviour

Polyflow should be robust enough to handle an empty string as sort

Actual behaviour

Throws StringIndexOutOfBoundsException

(In case of exceptions provide full stack trace)

java.lang.StringIndexOutOfBoundsException: begin 0, end 1, length 0
    at java.base/java.lang.String.checkBoundsBeginEnd(String.java:4604) ~[na:na]
    at java.base/java.lang.String.substring(String.java:2707) ~[na:na]
    at io.holunda.polyflow.view.query.PageableSortableQuery$DefaultImpls.sanitizeSort(PageableSortableQuery.kt:33) ~[polyflow-view-api-4.0.0-20231010.140436-1.jar:4.0.0-SNAPSHOT]
    at io.holunda.polyflow.view.query.task.TasksWithDataEntriesForUserQuery.sanitizeSort(TasksWithDataEntriesForUserQuery.kt:17) ~[polyflow-view-api-4.0.0-20231010.140436-1.jar:4.0.0-SNAPSHOT]
    at io.holunda.polyflow.view.query.PageableSortableQuery$DefaultImpls.sanitizeSort(PageableSortableQuery.kt:21) ~[polyflow-view-api-4.0.0-20231010.140436-1.jar:4.0.0-SNAPSHOT]
    at io.holunda.polyflow.view.query.task.TasksWithDataEntriesForUserQuery.sanitizeSort(TasksWithDataEntriesForUserQuery.kt:17) ~[polyflow-view-api-4.0.0-20231010.140436-1.jar:4.0.0-SNAPSHOT