fix: Remove `cmd` only if exist (#12886)

* only remove cmd if exist

When calling this function from backend this line raises key error as there's no such key called cmd

* style: Simplify code

Co-authored-by: Suraj Shetty <13928957+surajshetty3416@users.noreply.github.com>

frappe/desk/treeview.py

@@ -66,7 +66,7 @@ def add_node():
 	doc.save()
 
 def make_tree_args(**kwarg):
-	del kwarg['cmd']
+	kwarg.pop('cmd', None)
 
 	doctype = kwarg['doctype']
 	parent_field = 'parent_' + doctype.lower().replace(' ', '_')