vim-patch:8.1.0181: memory leak with trailing characters in skip expression

Problem:    Memory leak with trailing characters in skip expression.
Solution:   Free the return value.
a43ebe9454

src/nvim/eval.c

@@ -991,6 +991,7 @@ static int eval_expr_typval(const typval_T *expr, typval_T *argv,
       return FAIL;
     }
     if (*s != NUL) {  // check for trailing chars after expr
+      tv_clear(rettv);
       emsgf(_(e_invexpr2), s);
       return FAIL;
     }

src/nvim/testdir/test_search.vim

@@ -325,6 +325,16 @@ func Test_searchpair_skip()
     bw!
 endfunc
 
+func Test_searchpair_leak()
+  new
+  call setline(1, 'if one else another endif')
+
+  " The error in the skip expression caused memory to leak.
+  call assert_fails("call searchpair('\\<if\\>', '\\<else\\>', '\\<endif\\>', '', '\"foo\" 2')", 'E15:')
+
+  bwipe!
+endfunc
+
 func Test_searchc()
   " These commands used to cause memory overflow in searchc().
   new