[chore] add test for handling undefined select value with spread

test/runtime/samples/spread-element-select-value-undefined/Select.svelte

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+<script>
+	export let options = [];
+	export let value = "";
+	export let label = "";
+</script>
+
+<select bind:value {...$$restProps}>
+	{#each options as option}
+		<option>{option}</option>
+	{/each}
+</select>
+<p>{label}</p>

test/runtime/samples/spread-element-select-value-undefined/_config.js

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+export default {
+	async test({ assert, component, target, window }) {
+		const select = target.querySelector('select');
+
+		assert.equal(select.value, '1');
+
+		component.label = 'hoge';
+
+		assert.equal(select.value, '1');
+	}
+};

test/runtime/samples/spread-element-select-value-undefined/main.svelte

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+<script>
+	import Select from "./Select.svelte";
+	let value = {
+		a: "1",
+		b: "1",
+	};
+	const options = ["1", "2", "3"];
+	export let label = "test";
+</script>
+
+<Select bind:value={value.a} {options} label={label} />