[PATCH net] lib: test_objagg: Set error message in check_expect_hints_stats()

Smatch complains that the error message isn't set in the caller:

    lib/test_objagg.c:923 test_hints_case2()
    error: uninitialized symbol 'errmsg'.

This static checker warning only showed up after a recent refactoring
but the bug dates back to when the code was originally added.  This
likely doesn't affect anything in real life.

Reported-by: kernel test robot <redacted>
Closes: https://lore.kernel.org/r/202506281403.DsuyHFTZ-lkp@intel.com/ (local)
Fixes: 0a020d416d0a ("lib: introduce initial implementation of object aggregation manager")
Signed-off-by: Dan Carpenter <redacted>
---
 lib/test_objagg.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/test_objagg.c b/lib/test_objagg.c
index a67b8ef5c5be..ce5c4c36a084 100644
--- a/lib/test_objagg.c
+++ b/lib/test_objagg.c

@@ -899,8 +899,10 @@ static int check_expect_hints_stats(struct objagg_hints *objagg_hints,
 	int err;
 
 	stats = objagg_hints_stats_get(objagg_hints);
-	if (IS_ERR(stats))
+	if (IS_ERR(stats)) {
+		*errmsg = "objagg_hints_stats_get() failed.";
 		return PTR_ERR(stats);
+	}
 	err = __check_expect_stats(stats, expect_stats, errmsg);
 	objagg_stats_put(stats);
 	return err;

-- 
2.47.2