Filter on a string which is null fails

[EwoutB99]

When applying a filter on a key of type string which is NULL the code goes into an error:
"Object reference not set to an instance of an object"

While this is not the case with DateTime. Unit tests also don't include the test with string values.

Example:

Filter the list on the value "abc" for key "name", with one record in the list having name = null will throw the error.
[1] = {[name, {"value": "abc" , "matchMode": "startsWith"}}]}