fix: don't move cursor to nil node

Author: mlysle

lua/treewalker/swap.lua

@@ -179,20 +179,27 @@ function M.swap_left()
   )
 end
 
+function bla(f, a, b, c, d, e, g)
+end
+
 ---@param node TSNode
 ---@param fn function
 function M.reorder(node, fn)
-  if not node then return nil end
+  if not node then return end
+  if not fn then return end
+
   ---@param iter TSNode
-  local iter = node
-  while fn(iter) do
+  local iter = fn(node)
+  while iter do
     operations.swap_nodes(fn(iter), iter)
     iter = fn(iter)
   end
-  -- place cursor on iter
+
+  -- We don't know which way we're swapping
+  local lastnode = nodes.prev_sib(iter) or nodes.next_sib(iter)
   vim.fn.cursor(
-    nodes.get_srow(iter),
-    nodes.get_scol(iter)
+    nodes.get_srow(lastnode),
+    nodes.get_scol(lastnode)
   )
 end