Allow switching to private channels with /join command (#6579)

webapp/components/confirm_modal.jsx

@@ -22,9 +22,7 @@ export default class ConfirmModal extends React.Component {
     }
 
     componentWillUnmount() {
-        if (!this.props.show) {
-            document.removeEventListener('keypress', this.handleKeypress);
-        }
+        document.removeEventListener('keypress', this.handleKeypress);
     }
 
     componentWillReceiveProps(nextProps) {