Add UltiSnipsFileType augroup and unset it if UltiSnips is disabled

autoload/UltiSnips.vim

@@ -16,10 +16,14 @@ endfunction
 
 call UltiSnips#bootstrap#Bootstrap()
 if !exists("g:_uspy")
-   " Delete the autocommands defined in plugin/UltiSnips.vim.
+   " Delete the autocommands defined in plugin/UltiSnips.vim and
+   " ftdetect/UltiSnips.vim.
    augroup UltiSnips
        au!
    augroup END
+   augroup UltiSnipsFileType
+       au!
+   augroup END
    finish
 end
 

ftdetect/UltiSnips.vim

@@ -1,5 +1,8 @@
 " This has to be called before ftplugins are loaded. Therefore
 " it is here in ftdetect though it maybe shouldn't
 if has("autocmd")
+   augroup UltiSnipsFileType
+      au!
       autocmd FileType * call UltiSnips#FileTypeChanged()
+   augroup END
 endif