add test for #3569 and similar situations

test/runtime/samples/binding-input-text-undefined/_config.js

@@ -0,0 +1,30 @@
+export default {
+	html: `
+		<input>
+	`,
+
+	ssrHtml: `
+		<input>
+	`,
+
+	async test({ assert, component, target, window }) {
+		const input = target.querySelector('input');
+		assert.equal(input.value, '');
+
+		component.x = null;
+		assert.equal(input.value, '');
+
+		component.x = undefined;
+		assert.equal(input.value, '');
+
+		component.x = 'string';
+		component.x = undefined;
+		assert.equal(input.value, '');
+
+		component.x = 0;
+		assert.equal(input.value, '0');
+
+		component.x = undefined;
+		assert.equal(input.value, '');
+	},
+};

test/runtime/samples/binding-input-text-undefined/main.svelte

@@ -0,0 +1,5 @@
+<script>
+	export let x;
+</script>
+
+<input bind:value={x}>