fix nvimtree vim globals not having any effect

lua/plugins/configs/nvimtree.lua

@@ -1,9 +1,4 @@
-local present, nvimtree = pcall(require, "nvim-tree")
-
-if not present then
-   return
-end
-
+-- globals must be set prior to requiring nvim-tree to function
 local g = vim.g
 
 g.nvim_tree_add_trailing = 0 -- append a trailing slash to folder names
@@ -40,6 +35,12 @@ g.nvim_tree_icons = {
    },
 }
 
+local present, nvimtree = pcall(require, "nvim-tree")
+
+if not present then
+   return
+end
+
 local default = {
    filters = {
       dotfiles = false,