Fix type error

And lint error

Author: artemave

bindModel.js

@@ -46,8 +46,9 @@ var inputTypeBindings = {
     var currentValue = binding.get()
 
     var options = []
+    var tagName
     children.forEach(function (child) {
-      const tagName = child.tagName && child.tagName.toLowerCase()
+      tagName = child.tagName && child.tagName.toLowerCase()
 
       switch (tagName) {
         case 'optgroup':

test/browser/hyperdomSpec.ts

@@ -1297,10 +1297,10 @@ describe('hyperdom', function () {
             return h('div',
               h('select',
                 {binding: [this, 'colour']},
-                h('optgroup', {label: 'common'}, [
+                h('optgroup', {label: 'common'},
                   h('option.red', {value: 'red'}, 'red'),
-                  h('option.blue', {value: blue}, 'blue')
-                ]),
+                  h('option.blue', {value: blue}, 'blue'),
+                ),
               ),
               h('span', JSON.stringify(this.colour)),
             )