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.
diff --git a/src/eval.c b/src/eval.c
index 26aa0e3..4423419 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -729,6 +729,7 @@
 	    return FAIL;
 	if (*s != NUL)  /* check for trailing chars after expr */
 	{
+	    clear_tv(rettv);
 	    EMSG2(_(e_invexpr2), s);
 	    return FAIL;
 	}
diff --git a/src/testdir/test_search.vim b/src/testdir/test_search.vim
index 9b078be..28f0463 100644
--- a/src/testdir/test_search.vim
+++ b/src/testdir/test_search.vim
@@ -324,6 +324,16 @@
     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
diff --git a/src/version.c b/src/version.c
index 7275901..e6a7d8b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -790,6 +790,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    181,
+/**/
     180,
 /**/
     179,