Cleanup: move variable assignment out of the loop

It never changes inside this function, so there's no need to recompute it with
every loop iteration.

pkg/gui/controllers/files_controller.go

@@ -1221,13 +1221,14 @@ func normalisedSelectedNodes(selectedNodes []*filetree.FileNode) []*filetree.Fil
 }
 
 func isDescendentOfSelectedNodes(node *filetree.FileNode, selectedNodes []*filetree.FileNode) bool {
+	nodePath := node.GetPath()
+
 	for _, selectedNode := range selectedNodes {
 		if selectedNode.IsFile() {
 			continue
 		}
 
 		selectedNodePath := selectedNode.GetPath()
-		nodePath := node.GetPath()
 
 		if strings.HasPrefix(nodePath, selectedNodePath+"/") {
 			return true