ui: fix error when reloading DataStoreContent

...when an entry is selected, that doesn't exist after the reload.

E.g. when one deletes selects a file within a snapshot and then clicks
the delete icon for said snapshot, focusRow would then fail and the
loading mask stay on until a reload.

Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>

www/DataStoreContent.js

@@ -232,8 +232,10 @@ Ext.define('PBS.DataStoreContent', {
 		    }
 		    return selected === id;
 		}, undefined, true);
-		view.setSelection(selection);
-		view.getView().focusRow(selection);
+		if (selection) {
+		    view.setSelection(selection);
+		    view.getView().focusRow(selection);
+		}
 	    }
 
 	    Proxmox.Utils.setErrorMask(view, false);