fix: null-coalesce getFacets() to prevent TypeError on special char search terms

[ahuininga-orisha]

When a customer searches for certain characters — such as 0, -, ", <, &, [, ], or ! — the Tweakwise search response may return null for the facets list. This caused a fatal PHP TypeError on the search results page, showing an error instead of results.

The fix adds a null-coalescing fallback so that when no facets are returned, an empty array is used instead. The rest of the filter initialisation continues normally, resulting in a search results page with no filters — rather than a crash.

Changes

File	What changed
Model/Catalog/Layer/FilterList/Tweakwise.php	Null-coalesce getFacets() to [] to prevent TypeError when API returns no facets

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Scenario 1 — Search with 0 as query

1. Navigate to the search results page with query q=0 (e.g. /catalogsearch/result/?q=0).
2. Verify the page loads without a PHP error or exception.
3. Verify that products (if any match) or an empty results state is shown — no 500 error.

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Scenario 2 — Search with special characters

1. Search for each of the following terms one at a time: -, ", <, &, [, ], !.
2. For each term, verify the search results page loads without a PHP TypeError.
3. Verify layered navigation renders (possibly with no filters if none are returned).

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Scenario 3 — Normal search still works

1. Search for a regular product keyword (e.g. a product name or category term).
2. Verify search results load correctly with filters/facets displayed as expected.
3. Confirm no regression in filter behaviour.

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