ui: fix opening settings window in datastore panel

When a user directly opened the webui with a fragment that is not
the summary, opening of the 'my settings' window fails because the
initial set of the columns field triggers a state change, which in turn
tries to trigger 'updateColumns'. That fails though, since the columns
were not even rendered yet (because we are on a different tab).

To fix this, simply return when the panel is not rendered yet.

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>

www/datastore/Summary.js

@@ -264,6 +264,9 @@ Ext.define('PBS.DataStoreSummary', {
 	    if (key !== 'summarycolumns') {
 		return;
 	    }
+	    if (!me.rendered) {
+		return;
+	    }
 	    Proxmox.Utils.updateColumns(me);
 	});