The invocation of a non-existing function should return null

[saig0]

Describe the bug
If I invoke a non-existing function, the engine returns a failure. But it should be more friendly and return null instead.

To Reproduce
Steps to reproduce the behavior:

1. Evaluate the following expression

non_existing_function(10)

2. Verify that the engine returns a failure:

failed to evaluate expression 'non_existing_function(10)': no function found with name 'non_existing_function' and 1 parameters

Expected behavior
According to the DMN spec, the invocation of a non-existing function should return null.

(DMN 1.4, chapter 10.3.2.13.2, page 120)

• Related TCK issue: Clarify null handling in FunctionInvocation dmn-tck/tck#539
• Related TCK test case: test: verify non-existing function invocation dmn-tck/tck#612

Environment

• FEEL engine version: 1.17
• Affects:
  • Camunda Automation Platform 7: [7.x]
  • Zeebe broker: [0.x]