Fix null error in no-single-element-style-arrays

[frw]

I'm using the ESLint plugin in VSCode, and when I'm in the middle of typing out my component style (e.g. <View style>) in VSCode, I'm getting the following error:

TypeError: Cannot read property 'expression' of null
Occurred while linting root\src\Component.tsx:72
    at JSXAttribute (root\node_modules\eslint-plugin-react-native\lib\rules\no-single-element-style-arrays.js:40:25)
    at root\node_modules\eslint\lib\linter\safe-emitter.js:45:58
    at Array.forEach (<anonymous>)
    at Object.emit (root\node_modules\eslint\lib\linter\safe-emitter.js:45:38)
    at NodeEventGenerator.applySelector (root\node_modules\eslint\lib\linter\node-event-generator.js:293:26)
    at NodeEventGenerator.applySelectors (root\node_modules\eslint\lib\linter\node-event-generator.js:322:22)
    at NodeEventGenerator.enterNode (root\node_modules\eslint\lib\linter\node-event-generator.js:336:14)
    at CodePathAnalyzer.enterNode (root\node_modules\eslint\lib\linter\code-path-analysis\code-path-analyzer.js:711:23)
    at root\node_modules\eslint\lib\linter\linter.js:954:32
    at Array.forEach (<anonymous>)

Although a style attribute with no value is technically not valid, no-single-element-style-arrays should silently ignore this and not throw an error.

[sonarqubecloud]

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[frw]

Hi @Intellicode, could you take a quick look at this?

[StantonMatt]

I took a local pass because this is a small crash fix and the PR branch does not report any hosted checks.

The one-line guard applies cleanly on current origin/master. I verified the reported case with a RuleTester fixture:

• current origin/master throws Cannot read properties of null (reading 'expression') on <App style>foo</App>
• the merged patch ignores the missing style value and still reports/fixes the existing single-element array case

I also ran the current-master merge simulation locally:

TMPDIR=.codex-tmp/npm-tmp npm_config_cache=.codex-tmp/npm-cache npm ci
./node_modules/.bin/mocha tests/lib/rules/no-single-element-style-arrays.js
npm test
git diff --check --cached

Those passed: the focused rule file had 8 passing tests, and the full suite had 129 passing tests.

The only thing I would add before merging is a committed regression test for <App style> in tests/lib/rules/no-single-element-style-arrays.js, so this editor/incomplete-JSX case stays covered. Behavior-wise, the fix looks right from this pass.