Merge pull request #411 from xdl/master

Fix for nonexistent dir/bookmarks given to NERDTree commands

lib/nerdtree/creator.vim

@@ -43,6 +43,11 @@ endfunction
 function! s:Creator.createPrimary(name)
     let path = self._pathForString(a:name)
     
+    "abort if exception was thrown (bookmark/dir doesn't exist)
+    if empty(path)
+        return
+    endif
+
     "if instructed to, then change the vim CWD to the dir the NERDTree is
     "inited in
     if g:NERDTreeChDirMode != 0