Array input to flow throwing a conversion error

[mellistibco]

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[] feature request
[] support request
[] general question

Current behavior (how does the issue manifest):
Activity has the following input param:

    {
      "name": "fieldNames",
      "type": "array",
      "required": true
    }

Throws the following error:

interface conversion: interface {} is nil, not []string

Expected behavior:
The error not to be thrown and the activity executes as expected.

Minimal steps to reproduce the problem (not required if feature enhancement):

What is the motivation / use case for changing the behavior?

Please tell us about your environment (Operating system, docker version, browser & web ui version, etc):

Flogo version (CLI & contrib/lib. If unknown, leave empty or state unknown): 0.5.3

Additional information you deem important (e.g. issue happens only occasionally):

[mellistibco]

resolved in TIBCOSoftware/flogo-lib#163