skip array literal length optimization in presence of spread (#2325)

src/compile/render-dom/wrappers/EachBlock.ts

@@ -92,9 +92,11 @@ export default class EachBlockWrapper extends Wrapper {
 
 		this.index_name = this.node.index || renderer.component.get_unique_name(`${this.node.context}_index`);
 
-		const fixed_length = node.expression.node.type === 'ArrayExpression'
-			? node.expression.node.elements.length
-			: null;
+		const fixed_length =
+			node.expression.node.type === 'ArrayExpression' &&
+			node.expression.node.elements.every(element => element.type !== 'SpreadElement')
+				? node.expression.node.elements.length
+				: null;
 
 		// hack the sourcemap, so that if data is missing the bug
 		// is easy to find