Merge pull request #123 from jszakmeister/fix-currenttag-on-unsupported-file

When switching to a buffer that is unsupported, clear current.

autoload/tagbar.vim

@@ -3068,6 +3068,7 @@ function! s:AutoUpdate(fname, force) abort
     " Don't do anything if the file isn't supported
     if !s:IsValidFile(a:fname, sftype)
         call s:LogDebugMessage('Not a valid file, stopping processing')
+        call s:known_files.setCurrent({})
         return
     endif