Preserve list contents when CSV column import is cancelled

[Chessing234]

Bug

Importing a multi-column CSV into a list monitor prompts for a column number. Cancelling that prompt deletes all existing list items (#7313).

Root cause

parseInt(prompt(msg), 10) returns NaN when the user cancels. Mapping rows with row[NaN - 1] yields undefined for every row, and the subsequent string filter produces an empty array that replaces the list.

Why this fix is correct

Return early when the prompt is cancelled or the column number is out of range, so setVariableValue is not called and the existing list is left unchanged.

Fixes #7313

Made with Cursor

[github-actions]

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