try to reduce memory leak (ticket #33016)

try to reduce memory leak (ticket #33016)

current stat (Japanese manual):

 351663 words of node memory still in use:
   22 hlist, 2 vlist, 7 rule, 12 glue, 116 kern, 5 penalty, 2 glyph, 162367 attr
ibute, 2452 glue_spec, 7887 attribute_list, 3 action, 1 write, 1 pdf_literal, 1
pdf_setmatrix, 2 pdf_save, 2 pdf_restore, 33 user_defined nodes