Empty result for filter expression returns array of null

[Christoph Burgmer]

Selector: $[?(@.key==43)]

Input:

[{"key": 42}]

Expected output:

[]

Actual output:

[null]

Compare https://cburgmer.github.io/json-path-comparison/. For reference, the output was generated by the program in https://github.com/cburgmer/json-path-comparison/tree/master/implementations/Rust_jsonpath_lib.