Address FileNotFoundError

[nickolashkraus]

This pull request addresses an issue that may arise when using nerdtree-git-plugin in conjunction with nerdtree, syntastic, and fzf.

"<redacted>" 247L, 6784C written
syntastic: error: checker output:
Traceback (most recent call last):
  File "/<redacted>/.vim/bundle/syntastic/syntax_checkers/python/compile.py", line 11, in <module>
    compile(open(argv[1]).read(), argv[1], 'exec', 0, 1)
FileNotFoundError: [Errno 2] No such file or directory: 'NERD_tree_1'

Problem

This only occurs, however, when opening a file with FZF or with :e, then opening NERDTree. This is caused by bug in s:FileUpdate (also addressed here.

When a file is opened in this way and the NERDTree is opened, the nodes are not populated and therefore b:NERDTree.root.findNode returns {}.

This causes execution to return without returning the to the previous window after a call to g:NERDTree.CursorToTreeWin().

This issue then manifests when Syntastic executes. Within the call stack, the filename is derived from the % register instead of the buffer number (which is used to determine the filetype and subsequent checkers). Since, % has been changed to NERD_tree_1, the checker, specifically the Python compiler, fails.

The solution is to refactor the function such that

exec l:altwinnr . 'wincmd w'
exec l:winnr . 'wincmd w'

are always called.

Solution