Fixed that luatexja.append_italic() created orphaned attribute lists.

Fixed that luatexja.append_italic() created orphaned attribute lists.

 21440 words of node memory still in use:
   21 hlist, 2 vlist, 6 rule, 5 glue, 116 kern, 4 penalty, 2 glyph, 4906 attribu
te, 2452 glue_spec, 252 attribute_list, 3 action, 1 write, 1 pdf_literal, 1 pdf_
setmatrix, 2 pdf_save, 2 pdf_restore, 37 user_defined nodes
   avail lists: 1:5,2:224875,3:3624,4:16650,5:6634,6:4956,7:10015,8:81,9:9416,10
:680