set workflow task result if the task template result is empty

[Amy0511]

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[amhudson]

@Amy0511 make sure you apply this fix to the essentials_v3_stable as this is our working branch.

[Amy0511]

@amhudson Thank you for your reminder. I create a new PR to apply the fix to essentials_v3_stable https://github.com/boomerang-io/flow.service.workflow/pull/274. Should I close this PR?

[amhudson]

@Amy0511 I think it's safe to close this one.

[Amy0511]

@amhudson Thanks and closed the PR.