fix determining which variables are initialised (#2635)

src/compile/utils/scope.ts

@@ -75,12 +75,10 @@ export class Scope {
 		if (node.kind === 'var' && this.block && this.parent) {
 			this.parent.add_declaration(node);
 		} else if (node.type === 'VariableDeclaration') {
-			const initialised = !!node.init;
-
 			node.declarations.forEach((declarator: Node) => {
 				extract_names(declarator.id).forEach(name => {
 					this.declarations.set(name, node);
-					if (initialised) this.initialised_declarations.add(name);
+					if (declarator.init) this.initialised_declarations.add(name);
 				});
 			});
 		} else {