Fix React warning by correctly wrapping the new team modal trigger button into a NavItem

src/browser/components/TabBar.jsx

@@ -90,21 +90,25 @@ class TabBar extends React.Component {
       width: '40px',
       color: '#999',
       fontWeight: 'bold',
-      margin: '6px 0 0',
+      margin: '0',
       borderRadius: '2px 2px 0 0',
       outline: 'none'
     };
 
     return (
-      <Button
-        id='tabBarAddNewTeam'
-        onClick={this.props.onAddServer}
-        style={tabButton}
-        className='btn-tabButton'
-        title='Add new server'
+      <NavItem
+        className='buttonTab'
       >
-        {'+'}
-      </Button>
+        <Button
+          id='tabBarAddNewTeam'
+          onClick={this.props.onAddServer}
+          style={tabButton}
+          className='btn-tabButton'
+          title='Add new server'
+        >
+          {'+'}
+        </Button>
+      </NavItem>
     );
   }
 }