[WC-3314] Combobox: mitigate issue with empty string to executeAction()

[r0b1n]

• Normalize empty string filterValue to undefined before passing to onChangeFilterInputEvent.execute() to prevent widget crash
• Add changelog entry for the fix

There is a test project in related WTF story. Check that after the change there is not crash when input is cleared.

[github-actions]

AI Code Review

⚠️ Approved with suggestions — low-severity items only, safe to merge

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What was reviewed

File	Change
packages/pluggableWidgets/combobox-web/src/hooks/useGetSelector.ts	Normalize empty string filterValue to undefined before executing action
packages/pluggableWidgets/combobox-web/CHANGELOG.md	Add [Unreleased] entry for the fix

Skipped (out of scope): dist/, pnpm-lock.yaml

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Findings

Low — filterValue || undefined coerces all falsy values, not just empty string

File: packages/pluggableWidgets/combobox-web/src/hooks/useGetSelector.ts line 16

Problem: filterValue || undefined converts any falsy value to undefined, not just "". For the current string | undefined type this is correct in practice, but an explicit check better documents intent and is immune to future type widening.

Fix:

filterInput: filterValue !== "" ? filterValue : undefined

Non-blocking — the current fix is correct for all values that can arrive here.

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Low — No regression test for the empty-string guard

File: packages/pluggableWidgets/combobox-web/src/hooks/useGetSelector.ts

Problem: There is no unit test asserting that an empty-string filterValue causes execute to be called with { filterInput: undefined }. Without a test the bug can silently regress.

Fix: Add tests using actionValue() from @mendix/widget-plugin-test-utils:

it("passes undefined when filterValue is empty string", () => {
    const action = actionValue();
    onInputValueChange(action, "");
    expect(action.execute).toHaveBeenCalledWith({ filterInput: undefined });
});
it("passes value through when filterValue is non-empty", () => {
    const action = actionValue();
    onInputValueChange(action, "foo");
    expect(action.execute).toHaveBeenCalledWith({ filterInput: "foo" });
});

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Positives

• CHANGELOG entry is user-facing only with no implementation detail leakage.
• Fix correctly checks canExecute and isExecuting before calling execute(), following the Mendix ActionValue contract.
• The change is minimal and surgical — only the one offending argument is touched.