Bad configuration on a step should not prevent the user from being able to fix it from the UI

[keevan]

For example, setting an expression for a SFTP step's private key path field, may not cause issues with validation, but may cause the dataflow to fail to load the "view.php" page, and the user cannot navigate to edit the step.

Sometimes, it affects the variable tree, and so editing the step values itself, may become "impossible", and so the step needs to be deleted and recreated.

Ideally, both scenarios shouldn't happen, and validation kicks in before the step is saved. But if the step's validation doesn't catch a particular usecase, then it should be resolvable from the UI.

I suspect the variable tree section should be wrapped to not display on error, but still allow the rest of the page to load and the user to submit corrected information.

If the dataflow chart fails to render the full flow because of some dataflow variable/expression issue, then similarly it should show an error, but still allow the user to edit steps and resolve possible issues.