blocks.js format is not checked

ATM if blocks.js is not syntactically correct, the workspacefactory editor and the task are broken.
It should checked when loaded in the workspace.

Start by tracing where blocks.js is loaded by the workspacefactory editor and the task. Reproduce the failure with syntactically invalid blocks.js, then identify how loading currently handles the file. Done means invalid syntax is detected before it breaks the editor or task, with the relevant behavior verified.

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