fix for JSX mode being difficult to assert over due to self-closing tags

Author: developit

src/index.js

@@ -108,7 +108,7 @@ export default function renderToString(vnode, context, opts, inner) {
 			if (!(opts && opts.allAttributes) && (name==='key' || name==='ref')) continue;
 
 			let hooked = opts.attributeHook && opts.attributeHook(name, v, context, opts);
-			if (hooked) {
+			if (hooked || hooked==='') {
 				s += hooked;
 				continue;
 			}

src/jsx.js

@@ -21,6 +21,8 @@ let prettyFormatOpts = {
 
 
 function attributeHook(name, value, context, opts) {
+	if (value==null) return '';
+
 	let indentChar = typeof opts.pretty==='string' ? opts.pretty : '\t';
 	if (typeof value!=='string') {
 		preactPlugin.context = context;