Auto merge of #25710 - pylbrecht:pattern.incomplete, r=jdm

Make CanvasRenderingContext2D.createPattern() return null for incomplete images

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`createPattern()` should return `null` if the passed `image` argument is not usable.

References:
- https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-createpattern
- https://html.spec.whatwg.org/multipage/canvas.html#check-the-usability-of-the-image-argument
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix part of #25331

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- [x] There are tests for these changes

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