vim-patch:8.1.1012: memory leak with E461

Problem:    Memory leak with E461.
Solution:   Clear the typeval. (Dominique Pelle, closes vim/vim#4111)
ab89d7ab89

src/nvim/eval.c

@@ -2369,6 +2369,7 @@ static char_u *get_lval(char_u *const name, typval_T *const rettv,
         /* Can't add "v:" variable. */
         if (lp->ll_dict == &vimvardict) {
           EMSG2(_(e_illvar), name);
+          tv_clear(&var1);
           return NULL;
         }