fix(list): prevents error when there are no child elements

Author: Robert Messerle

src/components/list/list.js

@@ -157,7 +157,9 @@ function mdListItemDirective($mdAria, $mdConstant, $timeout) {
 
       function postLink($scope, $element, $attr, ctrl) {
 
-        var proxies = [];
+        var proxies    = [],
+            firstChild = $element[0].firstElementChild,
+            hasClick   = firstChild && firstChild.hasAttribute('ng-click');
 
         computeProxies();
         computeClickable();
@@ -187,25 +189,25 @@ function mdListItemDirective($mdAria, $mdConstant, $timeout) {
           var children = $element.children();
           if (children.length && !children[0].hasAttribute('ng-click')) {
             angular.forEach(proxiedTypes, function(type) {
-              angular.forEach($element[0].firstElementChild.querySelectorAll(type), function(child) {
+              angular.forEach(firstChild.querySelectorAll(type), function(child) {
                 proxies.push(child);
               });
             });
           }
         }
         function computeClickable() {
-          if (proxies.length || $element[0].firstElementChild.hasAttribute('ng-click')) {
+          if (proxies.length || hasClick) {
             $element.addClass('md-clickable');
 
             ctrl.attachRipple($scope, angular.element($element[0].querySelector('.md-no-style')));
           }
         }
 
-        if (!$element[0].firstElementChild.hasAttribute('ng-click') && !proxies.length) {
-          $element[0].firstElementChild.addEventListener('keypress', function(e) {
+        if (!hasClick && !proxies.length) {
+          firstChild.addEventListener('keypress', function(e) {
             if (e.target.nodeName != 'INPUT') {
               if (e.keyCode == $mdConstant.KEY_CODE.SPACE) {
-                $element[0].firstElementChild.click();
+                firstChild.click();
                 e.preventDefault();
                 e.stopPropagation();
               }
@@ -216,9 +218,9 @@ function mdListItemDirective($mdAria, $mdConstant, $timeout) {
         $element.off('click');
         $element.off('keypress');
 
-        if (proxies.length) {
+        if (proxies.length && firstChild) {
           $element.children().eq(0).on('click', function(e) {
-            if ($element[0].firstElementChild.contains(e.target)) {
+            if (firstChild.contains(e.target)) {
               angular.forEach(proxies, function(proxy) {
                 if (e.target !== proxy && !proxy.contains(e.target)) {
                   angular.element(proxy).triggerHandler('click');