Iterator does not recognize my map attribute

[ecarlier-tibco]

I'm submitting a ... (check one with "x")

[x] bug report 
[] feature request
[] support request
[] general question

Current behavior (how does the issue manifest):
I am attaching my app json. I am using the javascript activity and trying to iterate over one output of this js activity. It seems that this output var is correctly mapped to a proper array in golang, but somehow, iterator doesn't like it.
I can see this in the DEBUG logs (note also that you do not see any error logs if you do not switch on the DEBUG logs, although the flow execution is marked as Failed)

2018-05-17 14:07:38.689 DEBUG  [flowmodel-simple] - Eval Iterator Task 'log_4'
2018-05-17 14:07:38.689 DEBUG  [engine] - AddAttr - name: _E.activity, type: string, value:log_4
2018-05-17 14:07:38.689 DEBUG  [engine] - AddAttr - name: _E.message, type: string, value:unsupported type '[map[payload:Hello] map[payload:my] map[payload:dear] map[payload:Flynn]]' for iterateOn
2018-05-17 14:07:38.689 DEBUG  [engine] - AddAttr - name: _E.type, type: string, value:unknown
2018-05-17 14:07:38.689 DEBUG  [engine] - AddAttr - name: _E.data, type: object, value:<nil>
2018-05-17 14:07:38.689 DEBUG  [engine] - AddAttr - name: _E.code, type: string, value:

Expected behavior:
It should iterate :-)

Minimal steps to reproduce the problem (not required if feature enhancement):
Just use my app json attached and post to http port 1885 with the following example body:

{
	"Sentence": "Hello my dear Flynn"
}

What is the motivation / use case for changing the behavior?
Trying to re-use parts of apps developed with node-red

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

Flogo version (CLI & contrib/lib. If unknown, leave empty or state unknown): 0.X.X
flogo cli version [v0.5.3-16-g80636ce]
Did use flv switch to github.com/TIBCOSoftware/flogo-lib/engine@master,github.com/TIBCOSoftware/flogo-contrib/action/flow@master

flogo-splitflow.json.zip

[mellistibco]

Resolved in TIBCOSoftware/flogo-contrib#273