Remove open buffer from known files on bdelete or bwipe (#768)

Closes #750

On `:bdelete` or `:bwipe` of a file, remove the file from the known file
listing even if the tagbar window is not open. Previously was only
removing the file if the tagbar window was open.

autoload/tagbar.vim

@@ -3463,13 +3463,13 @@ function! s:HandleBufDelete(bufname, bufnr) abort
         return
     endif
 
+    call s:known_files.rm(fnamemodify(a:bufname, ':p'))
+
     let tagbarwinnr = bufwinnr(s:TagbarBufName())
     if tagbarwinnr == -1 || a:bufname =~# '__Tagbar__.*'
         return
     endif
 
-    call s:known_files.rm(fnamemodify(a:bufname, ':p'))
-
     if !s:HasOpenFileWindows()
         if tabpagenr('$') == 1 && exists('t:tagbar_buf_name')
             " The last normal window closed due to a :bdelete/:bwipeout.