DMN message construction for FEEL error throws NPE

When we call the FEEL function like string length(input), contains(input, pattern) or list contains(inputlist, input) and if input is NULL, it is throwing null pointer exception. Can the null be handled internally?

Let's consider a real time scenario, where we are validating the "Phone" number and the value is coming up dynamically. This input attribute is being used in a decision table for pattern matching.

Phone                                                                         Status

======                                                                    =====

not matches(?,"\d{10}")                                     "Phone is Invalid"

Everyone need not to have a Phone and now if the "Phone" attribute is missing or coming as NULL, it is throwing a null pointer exception. Ideally we are expecting "Phone is Invalid" status.