perf: optimize Path.getSortOrderIndex() method. (#1429)

* speedup: Path.getSortOrderIndex() optimisation.

* refactor: remove the redundant new line

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Co-authored-by: rzvxa <3788964+rzvxa@users.noreply.github.com>

lib/nerdtree/path.vim

@@ -362,9 +362,10 @@ endfunction
 " returns the index of the pattern in g:NERDTreeSortOrder that this path matches
 function! s:Path.getSortOrderIndex()
     let i = 0
+    let l:lpc = self.getLastPathComponent(1)
     while i < len(g:NERDTreeSortOrder)
         if g:NERDTreeSortOrder[i] !~? '\[\[-\?\(timestamp\|size\|extension\)\]\]' &&
-        \ self.getLastPathComponent(1) =~# g:NERDTreeSortOrder[i]
+        \ l:lpc =~# g:NERDTreeSortOrder[i]
             return i
         endif
         let i = i + 1