Fix select handler for main tab bar handled a click on the add server button (and failed)

src/browser/components/MainPage.jsx

@@ -142,6 +142,9 @@ const MainPage = React.createClass({
     }
   },
   handleSelect(key) {
+    if (key === 'addServerButton') {
+      return;
+    }
     const newKey = (this.props.teams.length + key) % this.props.teams.length;
     this.setState({
       key: newKey

src/browser/components/TabBar.jsx

@@ -98,6 +98,8 @@ class TabBar extends React.Component {
     return (
       <NavItem
         className='buttonTab'
+        key='addServerButton'
+        eventKey='addServerButton'
       >
         <Button
           id='tabBarAddNewTeam'