fix buffer mismatch in certain cases. resolves #715.

autoload/airline/extensions/tabline/formatters/unique_tail.vim

@@ -23,5 +23,10 @@ function! airline#extensions#tabline#formatters#unique_tail#format(bufnr, buffer
     let map[nr] = airline#extensions#tabline#formatters#default#wrap_name(nr, fnamemodify(bufname(nr), ':p:.'))
   endfor
 
-  return map[a:bufnr]
+  if has_key(map, a:bufnr)
+    return map[a:bufnr]
+  endif
+
+  " if we get here, the buffer list isn't in sync with the selected buffer yet, fall back to the default
+  return airline#extensions#tabline#formatters#default#format(a:bufnr, a:buffers)
 endfunction