Fix `ValueFromTransformer` without input deps

[GlassOfWhiskey]

Before this commit, a ValueFromTransformer without dependencies was not waiting for any input token, generating potential errors due to wrong token tags inside scatter and loop constructs. Now, a ValueFromTransformer without dependencies waits for all the other input ports to be available before being processed.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 69.95%. Comparing base (35a070a) to head (8e6cba9). Report is 2 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #553 +/- ## ========================================== + Coverage 69.92% 69.95% +0.03% ========================================== Files 87 87 Lines 10885 10888 +3 Branches 2549 2551 +2 ========================================== + Hits 7611 7617 +6 + Misses 2808 2805 -3 Partials 466 466 ```

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