Flow io.cloudslang.base.comparisons.equals does not accept an empty parameter

[pe-pan]

I'm trying to execute this flow:

namespace: io.cloudslang.demo
flow:
  name: test
  workflow:
    - is_empty:
        do:
          io.cloudslang.base.comparisons.equals:
            - first: 'a'
            - second: ''
        navigate:
            - 'TRUE': SUCCESS
            - 'FALSE': FAILURE
  results:
      - FAILURE
      - SUCCESS

It fails on

SEVERE: Command failed java.lang.RuntimeException: Failed compilation for file test.sl ,Exception is : java.lang.IllegalArgumentException: Cannot compile flow 'io.cloudslang.demo.test'. Step 'is_empty' does not declare all the mandatory inputs of its reference. The following inputs of 'io.cloudslang.base.comparisons.equals' are not private, required and with no default value: second.

How does one compare the argument with an empty string?

[pe-pan]

The workaround is to use io.cloudslang.base.strings.string_equals instead. Still I believe it's a bug.