add test of multiple styles; remove null styles;

src/runtime/internal/dom.ts

@@ -430,7 +430,11 @@ export function set_input_type(input, type) {
 }
 
 export function set_style(node, key, value, important) {
-	node.style.setProperty(key, value, important ? 'important' : '');
+	if (value === null) {
+		node.style.removeProperty(key);
+	} else {
+		node.style.setProperty(key, value, important ? 'important' : '');
+	}
 }
 
 export function select_option(select, value) {

test/runtime/samples/inline-style-directive-multiple/_config.js

@@ -0,0 +1,16 @@
+export default {
+	html: `
+	<p style="color: red; width: 65px; font-weight: 700;"></p>
+	`,
+
+	test({ assert, component, target, window }) {
+		const p = target.querySelector('p');
+
+		const styles = window.getComputedStyle(p);
+		assert.equal(styles.color, 'red');
+	},
+
+	skip_if_ssr: true
+	// SSR renders "null" string for null values:
+	// <p style="color: red; width: 65px; position: null; font-weight: 700;"></p>
+};

test/runtime/samples/inline-style-directive-multiple/main.svelte

@@ -0,0 +1,13 @@
+<script>
+	export let myColor = "red";
+	export let width = "65px";
+	export let absolute = false;
+	export let bold = true;
+</script>
+
+<p
+	style:color={myColor}
+	style:width
+	style:position={absolute ? "absolute" : null}
+	style:font-weight={bold ? 700 : 100}
+/>